Serena, Venus Williams Bounced from Doubles Competition at 2018 French Open

Serena Williams has suffered her first loss at Roland Garros since her comeback, losing in doubles competition Sunday alongside sister Venus to Andreja Klepac and Maria Jose Martinez Sanchez.

Klepac and Martinez Sanchez, who are the third-seeded pairing, earned a 6-4, 6-7 (4), 6-0 win over the Williams sisters. Venus had already been bounced out of singles competition at the French Open in the first round. Serena is set to square off against Maria Sharapova in a round-of-16 matchup Monday.

The Williamses dropped the first set and then trailed 5-4 in the second with Klepac and Martinez Sanchez serving for the match. However, they managed to battle back, winning three of the next four games—including the tiebreaker by a 7-4 margin.

But when the two pairs came back for a third set, the American duo fell apart. Klepac and Martinez Sanchez ran Venus and Serena off the court, dominating in every facet on their way to a 6-0 romp. It was clear both Serena and Venus ran out of gas during the second-set comeback, and it's also possible Serena was leaving something in the tank for her singles run.

"It's either play doubles or practice for two hours, so I'd rather play doubles," Serena told Christopher Clarey of the New York Times last week. "But the only difference is I'm actually getting in extra match play, and I'm really lacking match play. So I'm in a position where I need the matches."

While she's managed to be victorious in each of her matches, Serena looks understandably rusty on the court. She has shown flashes of brilliance but needed a first-set tiebreak against Kristyna Pliskova in Round 1 and dropped the first set to Ashleigh Barty in Round 2.

The French Open is just her third singles tournament since giving birth last September and first since a two-month hiatus following an terminated return in March.

Williams has won her last 18 singles matches against Sharapova but said Saturday she sees herself as an underdog. 

"Quite frankly, she's probably a favorite in this match, for sure," Williams told reporters. "You know, she's been playing for over a year now. I just started. So, I'm just really trying to get my bearings and trying to feel out where I am and see where I can go."

Williams and Sharapova are slated to play at 8:15 a.m. ET on Monday morning.