Mary Stoiana vs Katerina Siniakova

UMPIRY

Japan Open - OsakaQuarter-finalHardFri 23 Oct · ~14:30Center · After 2 matches

Mary StoianaWTA #114 · USA46%

VSToss-up

Katerina SiniakovaWTA #86 · CZE54%

Win probabilityWho is more likely to winToss-up

46%54%

No meaningful edge. Serve performance in the first set is the likeliest tiebreaker.

Umpiry ScoreMatchup strength, 0–10 · not a probability

Stoiana M.4.6/10

Heavy underdog

Siniakova K.5.7/10

Slight disadvantage

Why

Surface+240 Hard Elo edgeSupports Siniakova K.

Overall ratingOverall Elo 1846Supports Siniakova K.

Recent run4-match win streakAgainst the prediction · Stoiana M.

Head-to-headNo prior meetingsBoth players

This eventDidn't play here last yearBoth players

ELO1 802

Hard ELO1 699

Last 107–3

Age23

EarningsCareer $421K2026 $260K

ELO1 900

Hard ELO1 764

Last 105–5

Age30

EarningsCareer $18.2M2026 $3.3M

Mary Stoiana faces Katerina Siniakova in the Japan Open - Osaka quarter-final on hard. Katerina Siniakova is the paper favourite — ranked #86, a roughly 240-point hard Elo advantage — but Mary Stoiana arrives in form, winning 7 of their last 10 on hard to Katerina Siniakova's 5 of 10.

Key context

Serve & return: Katerina Siniakova brings the bigger serve (Serve Rating 28), Mary Stoiana the stronger return game (Return Rating 62).
Last match: Katerina Siniakova dropped just 5 games past Magda Linette.
Fatigue load: Katerina Siniakova carries the heavier recent load — 2 three-setters to 1 in the past fortnight.

Common opponents

2 shared · last 12 months

Stoiana M. and Siniakova K. faced 2 of the same opponents in the last 12 months. Stoiana M. went 0–2 (0%) against them, Siniakova K. 1–1 (50%).

0–20%Stoiana M. · better vs 0Record vs common opponents1–150%Siniakova K. · better vs 1

Vs common opponents · derived from scorelines

1–4Sets2–3

17–30Games18–23

1–0Tiebreaks0–0

0–1Deciding sets0–0

Only 2 common opponents — too few for any conclusion. Shown without assessment.

vs Stearns P.#37L7-6(5) 0-6 4-6Memphis · hardW6-4 0-6 4-0Japan Open - Osaka · hard
vs Badosa P.#61L4-6 2-6Sao Paulo · hardL3-6 5-7Dubai · hard

Head-to-head

They have not met before.

Evidence

Stoiana M.Siniakova K.

FormLast 10 matches each · 2026

Win–loss7–35–5

Season win rate64% (44–25)49% (19–20)

RatingUmpiry ELO

Overall ELO18021900

Hard-court ELO16991764

Serve vs returnLast 65 vs 37 matches

1st-serve points won62%63%

Return points won46%43%

Aces / match1.61.9

ClutchLast 65 vs 37 matches

Break points saved55%59%

When it starts

Center · After 2 matches · Followed by

1Li A. v Tagger L.Starting at 11:30 AM
2Gibson T. v Krueger A.Followed by
3This match: Stoiana M. v Siniakova K.This match
4Boulter K. v Ruzic A.Followed by

Draw

Odds

Conditions

Center · ~14:30 local

SurfaceHard

Forecast22°C · Partly cloudy

Wind9 km/h

Humidity67%

Freshness

Last 7 & 14 days

Stoiana M.Siniakova K.

2Days since last match2

3Matches · 7 days1

61Games · 7 days20

3Matches · 14 days2

61Games · 14 days47

Green marks the fresher player.

Cite this

Umpiry, "Mary Stoiana vs Katerina Siniakova — Japan Open - Osaka Quarter-final", https://umpiry.com/match/2026-10-23/siniakova-vs-stoiana-japan-open-osaka-qf?utm_source=cite (as of 23 October 2026).