Compare 2–4 players through results, serve/return and shot volumes — with the sample behind each figure.
The period applies to surface records, serve/return and shot volumes. Annual trends, head-to-head and the cumulative profile have their own stated windows. Missing data are not zero.
Recorded historical meetings, independent of the selected period. Not a prediction.
Win percentages grouped by surface.
| Surface | Claire Liu | Marta Kostyuk |
|---|---|---|
| Hard | 61.8%21 won / 34 matches | 64.3%18 won / 28 matches |
| Clay | 60%12 won / 20 matches | 91.3%21 won / 23 matches |
| Grass | 50%2 won / 4 matches | 83.3%5 won / 6 matches |
Matches without a recognised surface are not assigned to a surface.
Annual win rate across all surfaces; current year incomplete. Independent of the period selector.
Three score-derived indicators, across surfaces and levels. Each needs at least 20 relevant events. This profile does not follow the period selector.
| Metric | Claire Liu | Marta Kostyuk |
|---|---|---|
| How they win and how they loseDerived from the score — covers every circuit, Challenger and ITF included. | ||
| Comes back after losing the 1st set | 21.8%n=87 | 30.2%n=106 |
| Closes out after winning the 1st set | 83.5%n=85 | 85.9%n=135 |
| Wins the tiebreak | 52.2%n=46 | 52.2%n=67 |
Five-year cumulative score profile, independent of the period selector. Comebacks count matches after losing set one; closeouts count matches after winning it; tiebreaks count tiebreaks. Each rate needs at least 20 events. “—” means unavailable or insufficient data, never zero.
Six observed rates, with opportunities and valid-match samples visible below.
Only valid numerator–denominator pairs from the same match contribute to each rate. Break conversion is derived from the opponent's break points faced minus those saved. The table shows the contributing counts and matches.
| Metric | Claire Liu | Marta Kostyuk |
|---|---|---|
| 1st Serve Win % | 61.8%1,725 / 2,790 opportunitiesn=54 matches | 70.4%1,358 / 1,930 opportunitiesn=47 matches |
| 2nd Serve Win % | 45.6%635 / 1,394 opportunitiesn=54 matches | 46.3%647 / 1,396 opportunitiesn=47 matches |
| 1st Return Won % | 39.3%298 / 759 opportunitiesn=19 matches | 41.4%422 / 1,019 opportunitiesn=22 matches |
| 2nd Return Won % | 60.1%309 / 514 opportunitiesn=19 matches | 56.7%312 / 550 opportunitiesn=22 matches |
| BP Saved % | 56.3%214 / 380 opportunitiesn=36 matches | 63.1%118 / 187 opportunitiesn=26 matches |
| BP Converted % | 48.5%178 / 367 opportunitiesn=36 matches | 49.4%118 / 239 opportunitiesn=26 matches |
Winners, aces, net points won and unforced errors per match. A description, not a skill score.
Index 100 = recorded circuit average in the selected period, pooling levels, surfaces and match formats. A larger area means more recorded shots or errors per match, not a better player.
Circuit reference: 20.6 · n=1,188
Circuit reference: 1.8 · n=29,494
Circuit reference: 8.1 · n=1,154
Circuit reference: 27.5 · n=1,190
Five matches is a plotting threshold, not a reliability guarantee. Each metric has its own sample. Counts per match also depend on match length.
These are observations from our match database, not an independent verification of every source record. Coverage varies by player and metric; some serve counts are reconstructed upstream from rounded percentages. Surface, opponent strength and match format are not adjusted for. Small samples and different schedules limit comparisons. Career means the history available in our database, not necessarily a complete career.
The weighted head-to-head percentage has been removed: its weights were not validated. Stored deciding-set, serve and partial-set indicators with calculation or coverage issues are withheld here pending upstream correction. Descriptive comparisons do not demonstrate predictive skill.