Game plan
Kiki Bertens v Marta Kostyuk
Every number combines what Kiki Bertens does well with what Marta Kostyuk allows, each measured against the tour average and shrunk toward it when the sample is thin. Flip perspective
Forecast
Each player's serve and return strength is fitted against every opponent they were charted against, so a record built on weak opponents counts for less. At least one of them is no longer active or has too little charted in the last three seasons, so both are compared on their careers. The result is then nudged by Kiki Bertens's record against Marta Kostyuk's tactical lookalikes and in their charted head-to-heads (lookalikes: +2.1 on serve, −3.3 on return vs expectation (452 points); head-to-head: −0.2 on serve, −10.6 on return vs expectation (144 points)). A game-by-game Markov chain turns point odds into match odds; the 90% range covers the uncertainty in the two strengths, not the nudges. Charted matches lean toward big events, so treat this as a scouting estimate, not a betting line.
Head to head, per 100 shots
| Career | Kiki | Marta |
|---|---|---|
| Direction choice | +0.08 ±0.04 better than 70% | −0.06 ±0.05 better than 43% |
| Shot selection | −0.41 ±0.09 better than 17% | +0.13 ±0.09 better than 60% |
| Execution | −0.19 ±0.21 better than 50% | −0.34 ±0.29 better than 41% |
| Points left on the table | 2.67 ±0.06 lower than 38% | 2.69 ±0.07 lower than 36% |
Each player's career against an average tour player in the same position, adjusted for opponent strength, with a 90% margin (shots clustered by match). Points left on the table is the gap to the best-value direction for the same stroke, so lower is better. Percentiles are within each player's own tour. A side is highlighted only when the gap is larger than the margin on the difference.
Serve plan
The share of points the server wins when a first serve lands in that direction (hover a rate for its 90% interval; ± is the 90% margin). "Matchup" combines the server's rate with how this returner handles that serve. "Optimal" is the mix that wins most against this returner once they start reading a habit, at the response measured across the tour, and only within the range servers' habits actually vary. The gain over the current mix is how exploitable that mix is.
Kiki Bertens serving
Deuce court
| 1st serve | Now | Kiki wins | v Marta | Matchup | Optimal |
|---|---|---|---|---|---|
| Wide | 49% | 71% | 63% | 68.8%±3.4 | 46% ▼ |
| Body | 9% | 62% | 57% | 61.2%±6.1 | 0% ▼ |
| T | 42% | 70% | 68% | 70.7%±3.8 | 54% ▲ |
Optimal v Marta Kostyuk: +0.2±0.5 per 100 first serves (faults included) over the current mix, inside the 90% margin. Serving T every time would read +1.8 per 100 first serves in before the returner adjusts.
Ad court
| 1st serve | Now | Kiki wins | v Marta | Matchup | Optimal |
|---|---|---|---|---|---|
| Wide | 56% | 70% | 64% | 68.5%±3.7 | 71% ▲ |
| Body | 5% | 50% | 58% | 52.0%±7.7 | 0% ▼ |
| T | 39% | 68% | 61% | 64.6%±3.9 | 29% ▼ |
Optimal v Marta Kostyuk: +0.4±0.6 per 100 first serves (faults included) over the current mix, inside the 90% margin. Serving wide every time would read +2.4 per 100 first serves in before the returner adjusts.
Marta Kostyuk serving
Deuce court
| 1st serve | Now | Marta wins | v Kiki | Matchup | Optimal |
|---|---|---|---|---|---|
| Wide | 36% | 70% | 66% | 70.6%±3.6 | 51% ▲ |
| Body | 24% | 60% | 59% | 61.5%±4.9 | 9% ▼ |
| T | 40% | 72% | 64% | 68.6%±4.0 | 40% |
Optimal v Kiki Bertens: +1.1±0.7 per 100 first serves (faults included) over the current mix. Serving wide every time would read +3.0 per 100 first serves in before the returner adjusts.
Ad court
| 1st serve | Now | Marta wins | v Kiki | Matchup | Optimal |
|---|---|---|---|---|---|
| Wide | 47% | 73% | 63% | 70.2%±3.7 | 62% ▲ |
| Body | 26% | 58% | 58% | 59.8%±5.1 | 11% ▼ |
| T | 27% | 64% | 64% | 64.0%±4.7 | 27% |
Optimal v Kiki Bertens: +0.6±0.7 per 100 first serves (faults included) over the current mix, inside the 90% margin. Serving wide every time would read +4.3 per 100 first serves in before the returner adjusts.
Return plan
Value of each return, in points per 100 returns against an average return of the same serve (direction, court, surface): the tour's result with that return, the returner's own edge with it, and what this server gives up when it comes back to that side. Returns with no charted direction are left out, so values compare with each other rather than with zero. Depth isn't a choice here: missed returns have no depth. Serve quality isn't charted, so a block through the middle partly reflects the serve that forced it.
Kiki Bertens returning
1st serve to the forehand
| Return | Now | Tour | Own | v Marta | Value |
|---|---|---|---|---|---|
| FH through the middle | 46% | +4.2 | +1.8 | +0.7 | +6.7±1.6 |
| FH crosscourt | 16% | +5.3 | +0.4 | −3.9 | +1.8±3.2 |
| FH slice through the middle | 15% | −6.7 | −4.0 | −0.7 | −11.4±2.1 |
| FH down the line | 12% | +1.5 | −1.2 | −2.7 | −2.4±3.7 |
| FH slice crosscourt | 10% | −6.6 | +1.5 | −3.3 | −8.4±2.6 |
Lean FH through the middle: +6.3±1.2 per 100 returns v the current mix (1802 returns charted)
1st serve to the backhand
| Return | Now | Tour | Own | v Marta | Value |
|---|---|---|---|---|---|
| BH through the middle | 43% | +6.0 | ±0.0 | −0.2 | +5.9±1.4 |
| BH crosscourt | 18% | +7.7 | +0.2 | −1.5 | +6.5±2.4 |
| BH slice through the middle | 15% | −6.2 | −0.2 | −2.3 | −8.7±2.1 |
| BH down the line | 14% | +2.2 | −2.0 | −2.8 | −2.6±3.5 |
| BH slice crosscourt | 5% | −4.2 | −0.9 | −3.6 | −8.6±3.0 |
Lean BH crosscourt: +5.5±2.2 per 100 returns v the current mix (2080 returns charted)
2nd serve to the forehand
| Return | Now | Tour | Own | v Marta | Value |
|---|---|---|---|---|---|
| FH through the middle | 45% | −3.2 | +1.1 | +0.3 | −1.8±2.2 |
| FH crosscourt | 35% | +0.5 | −1.1 | −2.3 | −2.8±3.4 |
| FH down the line | 15% | −0.6 | −0.8 | −2.4 | −3.7±4.7 |
| FH slice through the middle | 3% | −15.2 | +0.2 | +0.3 | −14.7±2.1 |
| FH slice crosscourt | 1% | −14.9 | +0.9 | −1.3 | −15.3±2.0 |
Lean FH through the middle: +1.2±1.8 per 100 returns v the current mix (483 returns charted, inside the 90% margin)
2nd serve to the backhand
| Return | Now | Tour | Own | v Marta | Value |
|---|---|---|---|---|---|
| BH through the middle | 40% | −2.6 | −0.4 | −0.1 | −3.1±1.9 |
| BH crosscourt | 32% | +1.5 | −0.4 | −2.8 | −1.7±2.7 |
| FH through the middle | 9% | −2.7 | −0.4 | +0.3 | −2.7±2.1 |
| FH inside-in | 8% | +0.7 | +1.3 | −2.3 | −0.3±4.0 |
| BH down the line | 7% | −0.5 | −2.9 | −1.3 | −4.7±5.1 |
Lean FH inside-in: +2.2±3.9 per 100 returns v the current mix (1083 returns charted, inside the 90% margin)
Marta Kostyuk returning
1st serve to the forehand
| Return | Now | Tour | Own | v Kiki | Value |
|---|---|---|---|---|---|
| FH through the middle | 41% | +4.2 | +0.6 | −1.0 | +3.7±1.6 |
| FH crosscourt | 19% | +5.3 | +0.5 | +0.5 | +6.3±3.1 |
| FH slice through the middle | 17% | −6.7 | +1.4 | −0.7 | −6.0±1.9 |
| FH down the line | 12% | +1.5 | +4.8 | −3.8 | +2.5±3.7 |
| FH slice crosscourt | 8% | −6.6 | +0.9 | −0.3 | −6.0±2.7 |
Lean FH crosscourt: +5.1±2.7 per 100 returns v the current mix (1346 returns charted)
1st serve to the backhand
| Return | Now | Tour | Own | v Kiki | Value |
|---|---|---|---|---|---|
| BH through the middle | 52% | +6.0 | −0.2 | −0.8 | +5.0±1.5 |
| BH crosscourt | 29% | +7.7 | −2.1 | −2.2 | +3.4±2.4 |
| BH down the line | 10% | +2.2 | −1.1 | −4.8 | −3.7±4.0 |
| BH slice through the middle | 4% | −6.2 | −0.1 | −0.4 | −6.6±2.2 |
| BH slice crosscourt | 3% | −4.2 | −0.7 | −3.0 | −7.8±2.8 |
Lean BH through the middle: +2.5±1.1 per 100 returns v the current mix (969 returns charted)
2nd serve to the forehand
| Return | Now | Tour | Own | v Kiki | Value |
|---|---|---|---|---|---|
| FH through the middle | 41% | −3.2 | +1.5 | +0.1 | −1.6±2.3 |
| FH crosscourt | 28% | +0.5 | −1.0 | −4.5 | −5.0±3.8 |
| FH down the line | 25% | −0.6 | +0.7 | −2.3 | −2.2±4.4 |
| FH slice through the middle | 4% | −15.2 | +0.6 | −0.4 | −15.0±2.2 |
| FH slice crosscourt | 2% | −14.9 | +0.6 | −0.8 | −15.1±2.1 |
Lean FH through the middle: +1.9±2.0 per 100 returns v the current mix (362 returns charted, inside the 90% margin)
2nd serve to the backhand
| Return | Now | Tour | Own | v Kiki | Value |
|---|---|---|---|---|---|
| BH through the middle | 46% | −2.6 | −2.6 | −0.9 | −6.1±1.8 |
| BH crosscourt | 30% | +1.5 | −1.1 | −2.1 | −1.8±2.7 |
| BH down the line | 19% | −0.5 | +1.0 | −2.9 | −2.4±4.4 |
| FH inside-out | 2% | +1.4 | ±0.0 | −2.3 | −1.0±3.1 |
| FH through the middle | 1% | −2.7 | −0.2 | +0.1 | −2.8±1.6 |
Lean BH crosscourt: +2.1±2.2 per 100 returns v the current mix (471 returns charted, inside the 90% margin)
Rally plan
Edge, in points per 100 shots: the hitter's skill with the shot (own) plus how much the receiver usually gives up against it (theirs), both measured against the tour average on hard. Each player's hard record is shrunk toward their all-surface one, so a thin sample on it moves the numbers only a little.
Kiki Bertens
Favour
| Shot | Edge | Own | Theirs |
|---|---|---|---|
| FH volley to their backhand · rally | +7.1±8.2 | +4.7 | +2.4 |
| BH to the middle · return +1 | +2.7±2.0 | +0.9 | +1.7 |
| BH to the middle · serve +1 | +2.1±2.0 | +1.4 | +0.6 |
| BH to the middle · return | +1.3±1.5 | −0.1 | +1.4 |
| BH volley to their backhand · rally | +1.1±8.6 | +2.8 | −1.8 |
| FH to their backhand · serve +1 | +1.0±2.6 | +1.0 | ±0.0 |
Avoid
| Shot | Edge | Own | Theirs |
|---|---|---|---|
| FH to their backhand · return | −8.0±3.5 | −3.4 | −4.6 |
| BH to their forehand · return | −7.7±4.0 | −3.9 | −3.9 |
| FH to their forehand · return | −6.8±3.0 | −2.8 | −4.0 |
| BH to their forehand · serve +1 | −6.1±4.7 | −4.0 | −2.1 |
| FH slice to the middle · rally | −5.9±3.2 | −1.3 | −4.6 |
Marta Kostyuk
Favour
| Shot | Edge | Own | Theirs |
|---|---|---|---|
| FH to the middle · return +1 | +3.1±2.3 | +2.2 | +0.9 |
| FH to their backhand · return +1 | +2.8±3.5 | +4.1 | −1.3 |
| FH to the middle · serve +1 | +2.5±1.8 | +2.1 | +0.5 |
| BH lob to the middle · rally | +2.3±4.1 | +1.7 | +0.5 |
| FH to their forehand · return +1 | +2.2±2.8 | +1.7 | +0.5 |
| FH slice to the middle · return +1 | +1.7±3.8 | +3.0 | −1.3 |
Avoid
| Shot | Edge | Own | Theirs |
|---|---|---|---|
| BH slice to their forehand · rally | −6.2±4.5 | −5.8 | −0.4 |
| BH to their forehand · return | −6.2±3.8 | −0.3 | −5.9 |
| BH to their forehand · return +1 | −5.2±5.2 | −5.8 | +0.7 |
| BH to their forehand · serve +1 | −4.6±4.8 | −3.1 | −1.5 |
| Smash to their backhand · rally | −4.1±8.1 | −0.3 | −3.9 |
Against Marta Kostyuk-like opponents
| Kiki Bertens v | Matches | Serve pts won | Return pts won |
|---|---|---|---|
| All charted opponents | – | 59.9% | 43.7% |
| Players most similar to Marta Kostyuk | 3 | 61.0% | 40.2% |
| Marta Kostyuk (charted head-to-head) | 1 | 57.3% | 31.4% |
Similar by tactical fingerprint: Alexandra Eala, Diana Shnaider, Xin Yu Wang, Bianca Andreescu, Leylah Fernandez, Jasmine Paolini, Olga Danilovic, Kaja Juvan, Katie Boulter, Nao Hibino. When two players have rarely met, their records against these lookalikes fill the gap.