Madrid - Venus Williams held off a late surge by Simona Halep to win 6-1, 4-6, 7-6 (8/6) in the first round of the Madrid Open on Saturday.
The seven-time major winner hit three aces and broke the Romanian twice en route to taking the first set.
But Halep rallied to take the second set before Williams could finally edge her out in the decisive tie-breaker.
"On the last match point I went for it. I wanted to leave it all out there on the court," said Williams, playing just her third tournament following a seven-month absence due to illness.
"A match like that can be good. We hit a lot of balls and I was able to get that clay-court mentality right away. I have to keep remembering I'm on clay."
Earlier, fifth-seeded Sam Stosur also needed three sets to beat Petra Martic.
Stosur saved six break points to claim the tight contest from the Croatian, 7-5, 4-6, 7-6 (7/5).
"Petra was playing really well, and it really went down to the wire today," said Stosur. "I thought my level got better and better as the match went on, and the last half of the third set was the best tennis we played."
Stosur will next face American Christina McHale, who converted five of 14 break points to beat Sweden's Sofia Arvidsson 6-4, 7-5.
"She's an up-and-coming young player who hits the ball well and is a great athlete," Stosur said. "I will have to be prepared and be on my game."
Also, eighth-seeded Li Na off China hit seven aces to ease by Gabrine Muguruza Blanco of Spain 6-2, 6-4.
Sorana Cirstea of Romania came from behind to upset seventh-seeded Marion Bartoli 6-7 (6/8), 6-4, 6-3, while Petra Cetkovska of the Czech Republic brushed by 10th-seeded Vera Zvonareva 6-2, 6-2.
Other winners included Mona Barthel of Germany, Klara Zakopalova of the Czech Republic, and local favourite Silvia Soler-Espinosa.
Results on Saturday from the Madrid Open at La Caja Magica (seedings in
Sorana Cirstea, Romania, def. Marion Bartoli (7), France, 6-7 (6/8), 6-4, 6-3.
Silvia Soler-Espinosa, Spain, def. Tamira Paszek, Austria, 6-7 (2), 6-2, 6-2.
Sam Stosur (5), Australia, def. Petra Martic, Croatia, 7-5, 4-6, 7-6 (7/5).
Petra Cetkovska, Czech Republic, def. Vera Zvonareva (10), Russia, 6-2, 6-2.
Venus Williams, United States, def. Simona Halep, Romania, 6-1, 4-6, 7-6 (8/6).
Christina McHale, United States, def. Sofia Arvidsson, Sweden, 6-4, 7-5.
Li Na (8), China, def. Gabrine Muguruza Blanco, Spain, 6-2, 6-4.
Mona Barthel, Germany, def. Julia Goerges, Germany, 6-4. 6-1.
Klara Zakopalova, Czech Republic, def. Iveta Benesova, Czech Republic, 6-4, 7-6 (7/5).