Dubai - Four-time Grand Slam champion Kim Clijsters lost her first match in her second tennis comeback on Monday following a 6-2, 7-6 (8/6) defeat to Garbine Muguruza in the opening round of the WTA event in Dubai.
Former world number one Clijsters, 36, had been out for seven years before the clash with world ranked 16 Muguruza, who reached the final of the Australian Open last month.
Spain's two-time Grand Slam winner Muguruza will play one of Veronika Kudermetova and Dayana Yastremska in the next round after having to fight off a determined Clijsters in a tight second set following a simple first.
"I've seen her play when I started on the tour, she's an incredible player," Muguruza said of Clijsters.
"I was excited to be the first (opponent of the comeback). She played very well, especially in the second set.
"At the end. It was very tight. It was a fun match to play.
"I'm sure she's going to get better and better, for sure she give me a lot of trouble. She played really well after all these years (away)."
Ninth seed Muguruza, 10 years younger than Clijsters, dominated early on as the veteran Belgian played her first official match since the 2012 US Open.
Mother of three Clijsters, who was playing in Dubai for the first time in her career, was on the back foot from the start, losing serve in the first game of both sets.
She found herself a two breaks down early in the second set after being swept aside in the first but fought back gamely to lead 5-4 after nine games.
However Muguruza took the set to a tie-break and emerged victorious with a service winner on her second match point after nearly an hour and three-quarters on court.
Earlier, Ons Jabeur beat Alison Riske 7-6 (7/3), 1-6, 6-3 to earn a second-round date with top seed Simona Halep.
Tunisian Jabeur, ranked 45 in the world, saw off American Riske amid passionate home support for a player who trains in Dubai.
"I'm so grateful for the crowd, they really gave me energy. It feels like home here," said Jabeur.
"Alison is tough, she made me run everywhere, I was down in the second set but got it back in the third," added the first Arab woman to reach a Grand Slam quarter-final last month at the Australian Open.
Barbora Strycova turned a corner after a poor start this season as she defeated US teenager Amanda Anisimova 7-6 (7/3), 2-6, 6-4, winning only her second match of 2020.
The 18-year-old Anisimova managed 43 winners but was weighed down by 67 unforced errors in a struggle lasting just over two-and-a-half hours.
"It wasn't really a great match from both sides, the balls were flying everywhere, it was a struggle to keep them on the court," the 33-year-old Strycova said.
"But I got through the match and I'm happy to be in the second round."
Strycova will face the winner between Su-Wei Hsieh and eighth-seed Petra Martic.