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# Stoiana vs Siniakova: Osaka model and market split
- URL: https://courtshark.ai/blog/stoiana-siniakova-osaka-model-market-split/
- Published: 2026-10-22T15:02:03.000Z
- Updated: 2026-10-22T15:02:02.000Z
- Description: Siniakova's ranking supports favoritism in Osaka, but Stoiana's recent form and return record make the case for a tighter contest.
- Author: Court Shark Desk
- Tags: match-preview, Mary Stoiana, Katerina Siniakova, Osaka 2026, Hard, Form

In this analysis

1. [Key takeaway](#key-takeaway)
2. [The disagreement is about the size of Siniakova's edge](#s-the-disagreement-is-about-the-size-of-siniakova-s-edge)
3. [Stoiana brings the stronger recent record](#s-stoiana-brings-the-stronger-recent-record)
4. [Watch whether Stoiana can pressure Siniakova's serve](#s-watch-whether-stoiana-can-pressure-siniakova-s-serve)
5. [Explore this matchup](#explore)
6. [Methodology and sources](#methodology)

Key takeaway

Siniakova has the stronger ranking, but Stoiana brings better recent results and more frequent breaks on hard courts. Whether that return pressure carries into this matchup is the key test.

52% is Court Shark's model probability for Katerina Siniakova in the Osaka quarterfinal, a narrow edge rather than a strong favorite's position. Her ranking supports favoritism, but Mary Stoiana's recent results and hard-court return record support a closer match.

## The disagreement is about the size of Siniakova's edge

The market consensus gives [Katerina Siniakova](https://courtshark.ai/players/katerina-siniakova-10211701) a 69% chance, leaving a 17 percentage point gap against Court Shark's estimate. Both favor her. The disagreement concerns how much separation there is between her and [Mary Stoiana](https://courtshark.ai/players/mary-stoiana-10223168), rather than which player should start as the favorite. That distinction matters for a match with evidence pointing in both directions.

The price moved 2 points toward Siniakova from the opening consensus. That establishes the direction of market expectations, but it cannot explain the reason for the move or identify which part of her game prompted it. The movement strengthened an existing preference rather than reversing the order of the players.

Siniakova is ranked No. 86, while Stoiana is No. 114\. That offers a straightforward basis for putting Siniakova ahead, although the ranking order alone does not establish how wide the difference should be on this surface. My reading is that her stronger standing supports the favorite's label. Stoiana's results provide the clearest argument against making that label too strong.

### Model and market on Mary Stoiana

Article snapshot, Oct 22, 2026 · Not live

Mary Stoiana's chance as the market consensus priced it from the opening line, next to the Court Shark model.

__Mary Stoiana's chance to win__
| Reading           | Mary Stoiana | Katerina Siniakova |
| ----------------- | ------------ | ------------------ |
| Opening consensus | 33%          | 67%                |
| Latest consensus  | 31%          | 69%                |
| Court Shark model | 48%          | 52%                |

Source: Court Shark model and pre-match market consensus.View data table

## Stoiana brings the stronger recent record

Stoiana has gone 7-3 over her latest matches, compared with Siniakova's 5-5\. Their recent hard-court records follow the same pattern, making Stoiana's form relevant to the conditions in Osaka rather than an achievement confined to another surface. Form favors Stoiana here. Those records do not adjust for opponent strength, so they cannot by themselves establish that she has played the better tennis.

Her four-match winning run includes a deciding set victory over Moyuka Uchijima after straight-set wins in her earlier Osaka matches. That is useful evidence of progress through this event, with her latest match requiring recovery after losing the middle set. It also means her current run has survived a setback within a match, rather than consisting entirely of uninterrupted control.

For Siniakova, a two-match winning run includes her latest victory over Magda Linette in straight sets. Her preceding victory over Peyton Stearns ended in a retirement, which limits how much that result says about her ability to finish a full contest. The Linette win is a cleaner positive signal. It gives Siniakova a current result to set against Stoiana's longer run, without erasing the broader contrast in recent consistency.

### Recent form

Article snapshot, Oct 22, 2026 · Not live

Each player's most recent completed matches, up to 10, oldest on the left.

__Recent results by player, oldest first__
| Player             | Date         | Result | Opponent               | Score              | Event            |
| ------------------ | ------------ | ------ | ---------------------- | ------------------ | ---------------- |
| Mary Stoiana       | Sep 2, 2026  | L      | Alexandra Eala         | 1-6 2-6            | US Open          |
| Mary Stoiana       | Sep 9, 2026  | W      | Jazmin Ortenzi         | 6-3 6-2            | Barranquilla 125 |
| Mary Stoiana       | Sep 10, 2026 | L      | Julia Riera            | 6-4 6-7(7) 3-6     | Barranquilla 125 |
| Mary Stoiana       | Sep 16, 2026 | W      | Claire Liu             | 6-3 7-5            | Sao Paulo        |
| Mary Stoiana       | Sep 17, 2026 | W      | Dominika Salkova       | 7-6(5) 6-1         | Sao Paulo        |
| Mary Stoiana       | Sep 18, 2026 | L      | Paula Badosa           | 4-6 2-6            | Sao Paulo        |
| Mary Stoiana       | Oct 17, 2026 | W      | Rinko Matsuda          | 6-3 7-6(1)         | WTA Osaka        |
| Mary Stoiana       | Oct 18, 2026 | W      | Sayaka Ishii           | 6-4 7-5            | WTA Osaka        |
| Mary Stoiana       | Oct 20, 2026 | W      | Oleksandra Oliynykova  | 6-2 6-3            | WTA Osaka        |
| Mary Stoiana       | Oct 22, 2026 | W      | Moyuka Uchijima        | 6-2 2-6 6-3        | WTA Osaka        |
| Katerina Siniakova | Aug 4, 2026  | L      | Kamilla Rakhimova      | 7-6(1) 0-6 2-5 RET | Toronto          |
| Katerina Siniakova | Aug 16, 2026 | W      | Jessica Bouzas Maneiro | 6-7(5) 6-1 6-1     | Cincinnati       |
| Katerina Siniakova | Aug 18, 2026 | L      | Madison Keys           | 1-6 3-6            | Cincinnati       |
| Katerina Siniakova | Aug 31, 2026 | W      | Elisabetta Cocciaretto | 6-3 6-2            | US Open          |
| Katerina Siniakova | Sep 3, 2026  | L      | Naomi Osaka            | 2-6 7-5 1-6        | US Open          |
| Katerina Siniakova | Oct 1, 2026  | W      | Magda Linette          | 6-4 6-3            | Beijing          |
| Katerina Siniakova | Oct 3, 2026  | L      | Elina Svitolina        | 6-1 4-6 2-6        | Beijing          |
| Katerina Siniakova | Oct 13, 2026 | L      | Liudmila Samsonova     | 1-6 7-5 2-6        | Wuhan            |
| Katerina Siniakova | Oct 20, 2026 | W      | Peyton Stearns         | 6-4 0-6 4-0 RET    | WTA Osaka        |
| Katerina Siniakova | Oct 22, 2026 | W      | Magda Linette          | 6-4 6-1            | WTA Osaka        |

Source: Court Shark model and match data.View data table

## Watch whether Stoiana can pressure Siniakova's serve

On hard courts, Stoiana has broken serve in 41% of return games, against Siniakova's 37%. That supports a concrete route for the underdog: keeping Siniakova from building comfortable service holds and making her defend repeatedly. Return pressure matters here. These samples cover different opponents and are not a direct measurement of how either player will return against the other.

On serve, Siniakova has held 66% of games in the hard-court sample, compared with Stoiana's 64%. I read that as a modest serving advantage rather than a decisive separation, especially alongside Stoiana's stronger return figure. Early service games should help test that reading. Comfortable holds for Siniakova would weaken the case that Stoiana can turn her return record into sustained pressure.

There is no previous meeting to establish a matchup pattern, so neither player has a direct record of solving the other's game. Watch whether Stoiana can protect serve while creating chances on return, rather than judging her prospects only by occasional breaks. If Siniakova repeatedly holds without pressure and attacks Stoiana's service games, the case for a close contest would become less persuasive.

## Explore this matchup

Compare both players side by side: recent results, surfaces, serve and return.

### Player comparison

Article snapshot, Oct 22, 2026 · Not live

Each measure on the same scale: recent wins, wins on this surface, head-to-head wins and the model's chance.

__Player comparison__
| Measure               | Mary Stoiana | Katerina Siniakova |
| --------------------- | ------------ | ------------------ |
| Wins, last 10 matches | 70% (7-3)    | 50% (5-5)          |
| Wins, last 10 on hard | 70% (7-3)    | 50% (5-5)          |
| Model win probability | 48%          | 52%                |

Source: Court Shark model and match data.View data table

### Win rate by surface

Article snapshot, Oct 22, 2026 · Not live

Share of matches won on each surface across each player's last 50 matches with full statistics.

__Win rate by surface__
| Surface | Mary Stoiana | Katerina Siniakova |
| ------- | ------------ | ------------------ |
| Hard    | 60% (15-10)  | 54% (20-17)        |
| Clay    | 67% (10-5)   | 50% (3-3)          |
| Grass   | 70% (7-3)    | 57% (4-3)          |

Source: Court Shark model and match data.View data table

### Serve and return on hard courts

Article snapshot, Oct 22, 2026 · Not live

How often each player held serve and broke serve on hard over their last 50 matches with full statistics, against the tour's all-years average on the surface.

__Hold and break rates on hard__
| Measure             | Mary Stoiana | Katerina Siniakova | Tour average, all years |
| ------------------- | ------------ | ------------------ | ----------------------- |
| Service games held  | 64%          | 66%                | 63%                     |
| Return games broken | 41%          | 37%                | 37%                     |
| Matches in sample   | 25           | 37                 |                         |

Source: Court Shark model and match data.View data table

### Model win probability

Article snapshot, Oct 22, 2026 · Not live

The Court Shark model's chance for each player to win this match.

__Model win probability by player__
| Player             | Win probability | Recent form (last 10) |
| ------------------ | --------------- | --------------------- |
| Mary Stoiana       | 48%             | 7-3                   |
| Katerina Siniakova | 52%             | 5-5                   |

Source: Court Shark model and match data.View data table

### Ways to win

Article snapshot, Oct 22, 2026 · Not live

Every way the match can finish. The likeliest single result is Katerina Siniakova in straight sets (34%).

__Chance of each final set score__
| Result                      | Chance |
| --------------------------- | ------ |
| Mary Stoiana wins 2-0       | 30%    |
| Mary Stoiana wins 2-1       | 18%    |
| Katerina Siniakova wins 2-1 | 18%    |
| Katerina Siniakova wins 2-0 | 34%    |

Source: Court Shark model and match data.View data table

### How long it could go

Article snapshot, Oct 22, 2026 · Not live

A 60% chance the match lasts 17 to 27 games; 21 is the middle of the range.

__Chance of each total number of games in the match__
| Total games | Chance |
| ----------- | ------ |
| 12          | 0.3%   |
| 13          | 1.2%   |
| 14          | 2.8%   |
| 15          | 5.0%   |
| 16          | 7.4%   |
| 17          | 8.7%   |
| 18          | 8.6%   |
| 19          | 7.9%   |
| 20          | 6.8%   |
| 21          | 5.1%   |
| 22          | 5.8%   |
| 23          | 3.7%   |
| 24          | 2.3%   |
| 25          | 3.8%   |
| 26          | 3.9%   |
| 27          | 3.8%   |
| 28          | 4.0%   |
| 29          | 4.1%   |
| 30          | 3.8%   |
| 31          | 3.3%   |
| 32          | 2.8%   |
| 33          | 1.8%   |
| 34          | 1.3%   |
| 35          | 1.1%   |
| 36          | 0.5%   |

Source: Court Shark model and match data.View data table

### Service games held: where they stand

Article snapshot, Oct 22, 2026 · Not live

Each dot is one of the WTA top 100 with enough matches in the last 52 weeks. Mary Stoiana ranks ahead of 1 of 64; Katerina Siniakova ranks ahead of 20 of 64.

__Service games held, last 52 weeks, against the WTA top 100__
| Player                      | Service games held | Place             |
| --------------------------- | ------------------ | ----------------- |
| Mary Stoiana                | 54.3%              | Ahead of 1 of 64  |
| Katerina Siniakova          | 66.4%              | Ahead of 20 of 64 |
| Field median                | 69.5%              |                   |
| Field best (Elena Rybakina) | 83.0%              | 1st               |

Source: Court Shark model and match data.View data table

### Two years of form

Article snapshot, Oct 22, 2026 · Not live

Each player's pre-match Elo rating since Jan 4, 2025\. Latest: Katerina Siniakova 1745 (Oct 20, 2026), Mary Stoiana 1708 (Oct 20, 2026).

__Pre-match Elo rating over the last two years__
| Player             | Start of window    | Two-year peak       | Latest              |
| ------------------ | ------------------ | ------------------- | ------------------- |
| Mary Stoiana       | 1500 (Jan 8, 2025) | 1708 (Oct 20, 2026) | 1708 (Oct 20, 2026) |
| Katerina Siniakova | 1675 (Jan 4, 2025) | 1787 (Oct 10, 2025) | 1745 (Oct 20, 2026) |

Source: Court Shark model and match data.View data table

[Explore this matchup](https://courtshark.ai/h2h?p1=10211701&p2=10223168)

Court Shark win probabilities are statistical estimates, not advice. No outcome is guaranteed.

Our forecast

Court Shark's model

Katerina Siniakova 52% to win

Match shape

Katerina Siniakova in straight sets: 34%

Deciding set: 36%

Total games: median 21, middle half 17 to 27

AI analyst

Picks Katerina Siniakova (agrees with the model)

Its case: Siniakova has faced markedly stronger recent opposition, her typical opponent was ranked 58 and 46% were top-50, versus 191 and 2.5% for Stoiana, and she brings a modest hard-court serving edge, winning 63.5% of first-serve points against 61.5%.

The risk it names: Stoiana is the bigger danger: she is 7-3 in her last 10 hard-court matches, on a four-match overall winning streak, and owns a 69.6% tiebreak win rate, but her 410 minutes over four matches this week is a tougher workload than Siniakova's 176 minutes over two.

Estimates recorded before play, not certainties.

Keep exploring

[Follow this match on Court Shark](https://courtshark.ai/matches?file=bdl%5F18821464)[Create a free account to keep it](https://courtshark.ai/register?redirect=%2Fmatches%3Ffile%3Dbdl%5F18821464)

Match context

Players

Mary Stoiana  
vs Katerina Siniakova

Event

Osaka

Surface

Hard

Round

Quarterfinal

Date

Friday, October 23

Article snapshot · Not live

Continue your research

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Related on Court Shark

- [How our match model works](https://courtshark.ai/blog/methodology/)
- [Open the full head-to-head](https://courtshark.ai/h2h?p1=10211701&p2=10223168)
- [Our editorial standards](https://courtshark.ai/blog/editorial-standards/)
- [About the desk](https://courtshark.ai/blog/about-the-desk/)

## Methodology and sources

How we build model estimates and where our information comes from.

Model estimates and observed results

The win probabilities come from the Court Shark match model, trained on completed ATP and WTA matches. A probability says how often a player in this position wins, not that one result will happen. The model's number for a match is recorded before play and never changed afterwards, so it can be checked against the result.

Sources and citations

Results, scores, rankings and serve statistics come from the Court Shark match database. The market consensus is the pre-match price for each player converted to a probability. Figures in this article are a snapshot taken when it was written.

Limitations

Serve and return rates count only matches with full serve statistics, which are sparser for Challenger and lower-level events, and the tour average they are compared with covers every year on record. Head-to-head records count every meeting with a recorded winner, walkovers and retirements included. Charts and tables are a snapshot and do not update after publication.

About the desk

Who works on the Tennis Desk and how an article is put together. [Read about the desk](https://courtshark.ai/blog/about-the-desk/)

Editorial standards

What we publish, what we check and how we decide what is fit to print. [Read our standards](https://courtshark.ai/blog/editorial-standards/)

Corrections

Spotted an error? Write to hello@courtshark.ai and we will correct it and note the change. [Read the corrections policy](https://courtshark.ai/blog/editorial-standards/)