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Serena Williams returned to competitive tennis on Saturday for the first time since giving birth, but she lost 10-5 in a first-to-10 tiebreak to Jelena Ostapenko in Abu Dhabi after an even first two sets.

A four-game run was crucial to Ostapenko's taking the first set 6-2. Williams responded in the second and won 6-3, showing flashes of her best to level things. The 2017 French Open champion took the deciding match tiebreak, though.

Williams was last on court in January, when she beat sister Venus in the final of the Australian Open. It was later revealed Williams was eight weeks pregnant when she won the title Down Under.

Afterwards, Williams said it at first felt strange to play again, per Live Tennis:

Given Williams has been away from the court for so long, the early stages of the contest were always going to make for fascinating viewing. She got off to a flier.

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The 23-time Grand Slam champion was on the front foot immediately, conjuring three break points against the Latvian's serve. She took the second one to edge in front.

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Williams didn't make a similar impression on serve, though, as Ostapenko broke back. Ostapenko then consolidated with a hold and got stuck into Williams' delivery again.

By the end of the fourth game, Williams had only won one point on her serve. As relayed by journalist Reem Abulleil, the 36-year-old looked understandably rusty:

Another hold by Ostapenko gave the American a mountain to climb in the first set at 4-1 down, although she secured her first hold of serve in the match.

Still, Ostapenko looked like the stronger player and clinched the opening set, breaking Williams' serve for the third time.

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In the second set, Williams again started with a break, although this time she put the hammer down. The American held serve and then broke again, opening up some daylight to her opponent.

Ostapenko came back, winning the next two games. But Williams was growing into the match and kept her opponent at bay, taking the second set. Here's how she did it, per EurosportUK:

In the end, Ostapenko had the most energy after an hour's play, and she earned what'll be a confidence-boosting victory in the tiebreak.

Williams, meanwhile, is experienced enough to know there are many more steps to take before she embarks on the defence of her Australian Open crown in the new year.