RallyIQ

WTA · Right-handed · 121 charted matches · 2012–2021

Kiki Bertens

Archetype: Ad-court slider · Avoids the wide serve

Against an average opponent

Serve points won 60.5% ±2.3 raw 60.0% · tour 56.3% · 8,461 points
Return points won 46.2% ±2.4 raw 43.7% · tour 43.7% · 8,724 points

Serve and return points won, refitted against every opponent at once so a record built on weak or strong opposition is put on the same scale. Career, all surfaces, with a 90% margin. Raw is the plain share of points won.

Value per 100 shots

Direction choice +0.08 ±0.04 better than 70% of WTA · raw +0.08
Shot selection −0.41 ±0.09 better than 17% of WTA · raw −0.40
Execution −0.19 ±0.21 better than 50% of WTA · raw −0.14
Tactical adaptability −0.15 first serves toward what's working, set to set · 117 matches
Adaptation speed −0.01 same, every two to three service games · per 100 first serves
Points left on the table 2.67 per 100 shots vs best direction · lower than 38% of WTA

Points gained per 100 shots compared with an average tour player in the same position, adjusted for the strength of the opponents faced, with a 90% margin (shots clustered by match). Raw is before the opponent adjustment. Built on 46,122 shots.

Shot expected value

The share of points Kiki Bertens goes on to win after each option in the positions they face most often, shrunk toward tour average when the sample is small. Showing the 8 most-used options; teal marks the best one with at least 30 shots.

Rally, shots 5–8: drive to your backhand side

position worth 45% to the average player · 3,020 shots

OptionUsedWin %Tour
BH through the middle 28% 44.7%±2.8 43.3%
BH crosscourt 24% 44.6%±3.0 47.6%
BH slice through the middle 15% 36.8%±3.7 34.4%
BH slice crosscourt 11% 45.5%±4.3 40.4%
BH down the line 9% 40.5%±4.7 46.8%
FH inside-out 2% 47.3%±8.5 52.5%
BH slice down the line 2% 35.9%±8.2 31.7%
BH drop shot crosscourt 2% 43.7%±9.2 47.5%

Rally, shots 5–8: drive to your middle

position worth 50% to the average player · 2,499 shots

OptionUsedWin %Tour
FH crosscourt 29% 56.0%±3.0 52.7%
BH through the middle 17% 42.6%±3.9 46.2%
FH down the line 14% 49.7%±4.2 52.2%
FH through the middle 14% 43.9%±4.2 45.8%
BH crosscourt 13% 55.0%±4.5 50.9%
BH down the line 4% 47.7%±7.2 50.0%
BH slice through the middle 2% 46.3%±9.9 44.8%
FH down the line + approach 2% 63.5%±10.1 68.6%

Rally, shots 5–8: drive to your forehand side

position worth 43% to the average player · 2,440 shots

OptionUsedWin %Tour
FH crosscourt 47% 52.3%±2.4 46.7%
FH through the middle 22% 45.6%±3.5 41.3%
FH down the line 15% 41.4%±4.2 44.9%
FH slice through the middle 7% 30.5%±5.6 29.2%
FH slice crosscourt 4% 42.6%±7.6 31.9%
FH lob through the middle 2% 43.9%±9.9 29.4%
FH slice down the line 1% 17.6%±8.4 24.3%
FH lob down the line 1% 41.4%±11.8 27.3%

Return +1: drive to your middle

position worth 50% to the average player · 1,509 shots

OptionUsedWin %Tour
FH crosscourt 30% 52.1%±3.8 52.3%
FH through the middle 17% 50.1%±5.0 46.5%
BH through the middle 16% 42.8%±5.0 46.2%
FH down the line 12% 49.8%±5.9 53.0%
BH crosscourt 11% 50.1%±6.0 50.8%
BH down the line 5% 50.1%±8.8 50.6%
BH slice through the middle 2% 52.9%±10.9 45.9%
FH down the line + approach 2% 72.0%±10.8 69.2%

Serve under pressure

Pressure predictability index +4 How much less varied Kiki Bertens's first-serve direction gets on break points. Positive means easier to read. Based on 841 break-point first serves.

Deuce court

1st serveUsageBreak ptWon when in
Wide 49% 55% 71% / 66%
Body 9% 5% 62% / 57%
T 42% 41% 70% / 68%

4,181 normal · 212 break-point 1st serves

Ad court

1st serveUsageBreak ptWon when in
Wide 56% 57% 70% / 66%
Body 6% 5% 50% / 56%
T 39% 38% 68% / 64%

3,393 normal · 629 break-point 1st serves

Is the serve mix in equilibrium?

Game theory says a well-mixed server wins equally often with every direction they use. If one direction wins more, it's underused and points are being left behind. This is the minimax test Walker and Wooders ran on Wimbledon finals, applied to every charted first serve. Win rates include faults. "Optimal" allows for returners reading a habit. A direction loses 0.19 points per 100 serves for every 10 points of habitual usage, measured from WTA servers whose mix drifted between matches. Shifts stay within the range servers' habits actually vary, the only range that response was measured over.

Deuce court

1st serveUsagePoints wonOptimal
Wide49% 59.9%±1.7 n=2,167 49%
Body9% 62.0%±4.0 n=378 0% ▼
T42% 60.5%±1.9 n=1,848 51% ▲

Consistent with an optimal mix (p = 0.69).
Optimal mix: +0.2 per 100 first serves.

Ad court

1st serveUsagePoints wonOptimal
Wide56% 60.1%±1.7 n=2,242 67% ▲
Body5% 54.3%±5.2 n=221 0% ▼
T39% 59.2%±2.0 n=1,559 33% ▼

Consistent with an optimal mix (p = 0.14).
Optimal mix: +0.4 per 100 first serves.

Exploitability 0.32 points per 100 first serves What the optimal mix would win over the current one, both courts. More exploitable than 100% of WTA servers. Tested on matches they weren't fitted on, WTA mixes picked this way win 0.42 per 100 first serves on average.

Repeating the previous direction to the same court: −0.1±1.9 points per 100 against switching. Negative means returners read repeats. Tour-wide, repeating costs women about 0.4 points per 100 and costs men nothing, so men's returners don't measurably anticipate direction. (3,086 repeats, 5,087 switches.)

Return by serve direction

Return points won against each serve direction, compared with the tour average.

ServeCourtDirectionPointsWonvs tour
1stAd courtBody 533 42% −1.6±3.4
1stAd courtT 785 36% +0.1±2.8
1stAd courtWide 1,245 37% +2.8±2.2
1stDeuce courtBody 601 41% −1.6±3.2
1stDeuce courtT 1,014 36% +3.4±2.4
1stDeuce courtWide 1,202 34% −0.2±2.2
2ndAd courtBody 643 56% +1.3±3.1
2ndAd courtT 220 53% −1.6±5.2
2ndAd courtWide 741 53% −0.9±3.0
2ndDeuce courtBody 795 55% +0.7±2.8
2ndDeuce courtT 513 55% −1.4±3.5
2ndDeuce courtWide 404 56% +1.8±3.9

Signature patterns

Recurring sequences that win more than Kiki Bertens's own baseline, ranked by edge weighted by how often they're used.

Serve → +1

  1. Wide serve (deuce court) → FH crosscourt used 3.1% · won 57% · −7.4±5.0 vs own baseline
  2. Wide serve (ad court) → FH crosscourt used 2.0% · won 54% · −9.8±6.0 vs own baseline
  3. Body serve (deuce court) → FH crosscourt used 2.8% · won 55% · −8.8±5.2 vs own baseline
  4. T serve (ad court) → FH crosscourt used 2.3% · won 51% · −13.0±5.7 vs own baseline
  5. Wide serve (deuce court) → FH down the line used 2.2% · won 51% · −13.4±5.8 vs own baseline

Return

  1. vs T serve (deuce court) → BH through the middle, deep used 2.3% · won 58% · +15.8±5.6 vs own baseline
  2. vs T serve (deuce court) → BH through the middle, mid used 2.9% · won 53% · +10.4±5.1 vs own baseline
  3. vs wide serve (deuce court) → FH through the middle, deep used 2.1% · won 54% · +11.6±5.9 vs own baseline
  4. vs wide serve (ad court) → BH crosscourt, mid used 3.4% · won 51% · +8.8±4.7 vs own baseline
  5. vs wide serve (ad court) → BH through the middle, deep used 3.2% · won 52% · +9.1±4.9 vs own baseline

Rally, consecutive own shots

  1. FH crosscourt → FH crosscourt used 6.6% · won 56% · +8.6±3.0 vs own baseline
  2. BH crosscourt → FH crosscourt used 1.7% · won 60% · +12.9±5.6 vs own baseline
  3. FH down the line → FH down the line used 1.1% · won 54% · +7.1±7.0 vs own baseline
  4. FH through the middle → FH crosscourt used 2.8% · won 51% · +4.3±4.6 vs own baseline
  5. FH crosscourt → BH crosscourt used 2.3% · won 52% · +4.6±5.1 vs own baseline

Discovered sequences

Mined from every me → opponent → me run of three shots, with no templates. Ranked by how much more often Kiki Bertens wins the point once the sequence happens, weighted by how often it happens. Think of them as chess openings.

  1. FH down the line + approach → BH lob through the middle → Smash crosscourt used 0.1% · won 73% · +25.8±10.0 vs own baseline · +9.0 vs tour on the same sequence Disrupted by Ashleigh Barty (8/8)
  2. BH crosscourt → BH through the middle → FH crosscourt used 0.5% · won 59% · +11.3±7.0 vs own baseline · +7.6 vs tour on the same sequence Disrupted by Donna Vekic (4/8), Sara Errani (4/6)
  3. FH crosscourt → FH through the middle → FH crosscourt used 1.0% · won 55% · +7.9±5.3 vs own baseline · +1.1 vs tour on the same sequence Disrupted by Arina Rodionova (2/8), Garbine Muguruza (4/10)
  4. FH crosscourt → BH crosscourt → FH crosscourt used 0.5% · won 57% · +9.8±7.2 vs own baseline · +11.5 vs tour on the same sequence Disrupted by Marketa Vondrousova (2/6), Bernarda Pera (4/9)
  5. FH through the middle → FH through the middle → BH crosscourt used 0.2% · won 61% · +13.6±9.3 vs own baseline · +19.0 vs tour on the same sequence
  6. FH crosscourt → FH crosscourt → FH crosscourt used 2.4% · won 51% · +3.8±3.4 vs own baseline · +3.2 vs tour on the same sequence

Strengths and vulnerabilities

Value per 100 shots compared with the average player hitting (strengths) or facing (vulnerabilities) the same shot. Only shot types seen at least 120 times.

Hurts opponents most with

FH slice to their forehand · return+2.1192
FH slice to their backhand · rally+1.7171
FH to the middle · return +1+1.4621
BH to the middle · serve +1+1.3696
FH to the middle · return+1.11,734

Most exposed to

T 2nd serve · deuce court−2.3513
BH to their forehand · return +1−1.2291
BH to their backhand · return +1−0.5620
FH to the middle · return +1−0.3510
Wide 2nd serve · ad court−0.2741

Active players who are best at the shot in the top weakness: Madison Keys, Ons Jabeur, Iva Jovic, Caroline Wozniacki, Caroline Garcia

Tactical fingerprint

Each bar shows how far a style trait is from the WTA average, in standard deviations.

Drop shots / shot3.3%
Wide serves · ad56%
Wide serves · deuce49%
Backhand slice29%
T serves · deuce42%
Through the middle31%
Points at net9%
Run-around forehands10%
Forehand share55%
Chipped returns14%
Avg rally length4.3
T serves · ad39%
Serve & volley1%
Deep returns32%
Unforced errors / shot10.2%
Point-ending shots22.4%
FH down the line26%
1st serve in59%
BH down the line17%

Plays most like

  1. Petra Martic 2010–2024 plan v
  2. Anastasija Sevastova 2011–2025 plan v
  3. Karolina Muchova 2019–2026 plan v
  4. Xin Yu Wang 2019–2026 plan v
  5. Linda Klimovicova 2022–2026 plan v
  6. Marta Kostyuk 2018–2026 plan v
  7. Kaja Juvan 2018–2026 plan v
  8. Alison Van Uytvanck 2015–2022 plan v

Closest from another era

  1. Lindsay Davenport 1995–2006
  2. Monica Seles 1990–2003
  3. Martina Hingis 1996–2007

Charted matches