Two-time Australian Open champion Victoria Azarenka beat Latvian former French Open champion Jelena Ostapenko in the first round in Paris.
Azarenka, 43rd in the world, won 6-4 7-6 (7-4) in a match full of twists.
Neither player managed to hold serve until the ninth game, when Azarenka moved 5-4 up in the opening set.
The Belarusian had two match points saved in the second and was broken for a second time before she won the deciding tie-break.
Latvian world number 39 Ostapenko, who won the title at Roland Garros in 2017, has now been knocked out in the first round for the third time in four years.
It is also the second successive Grand Slam tournament at which she has failed to make the second round.
Azarenka, who has beaten Czech fourth seed Karolina Pliskova and Ukrainian fifth seed Elina Svitolina on clay in the past month, could face world number one Naomi Osaka in the next round.