Steffi Graf defeated Monica Seles 1-6 6-4 6-4 in the WTA Tour Championships quarter-final on carpet. The upset overturned the form book — Monica Seles came in defending last year's round of 16. Steffi Graf extended the head-to-head to 2–1.
| Date | Tournament | Round | Surface | Winner | Score |
|---|---|---|---|---|---|
| 1999-05-24 | Roland Garros | SF | clay | Steffi Graf | 6-7(2) 6-3 6-4 |
| 1999-01-18 | Australian Open | QF | hard | Monica Seles | 7-5 6-1 |
Averages over each player's completed matches in the selected window. ATP, WTA & Challenger.