Two Grand Slam champions were among those players scheduled in the first second-round matches of the day at Roland-Garros on Thursday, and while Sofia Kenin advanced in straight sets, Ashleigh Barty's tournament is over.

First on Court 14 at 11 a.m., No.4 seed Kenin overcame fellow American Hailey Baptiste, a qualifier who won four matches in Paris in her French Open debut, 7-5, 6-3. An hour later, top seed Barty took to Court Philippe-Chatrier against Poland's Magda Linette - but after revealing following her first-round victory that she injured her left hip days before the tournament began, Barty proved unable to overcome it.

"It's heartbreaking," Barty told reporters about the abrupt end to her fortnight. "I mean, we have had such a brilliant clay court season, and to kind of get a little bit unlucky with timing more than anything to have something kind of acute happen over the weekend and just kind of run out of time against the clock is disappointing. It won't take away the brilliant three months that we have had, as much as it hurts right now.

"We did everything, absolutely everything we could to give myself a chance. It was a small miracle that we were able to get on court for that first round."

Again arriving on court with her left leg wrapped, Barty appeared hampered on serve and with movement from the match's earliest stages: though she saved three break points in her first service game to level at 1-1, Linette ran off five straight games to wrap up a one-set lead in 36 minutes. 

The Aussie received off-court treatment after the first set, but only played on a little longer into the second: after Linette held serve to bring the score to 6-1, 2-2, Barty walked to the net to shake hands.

"I just tried to give myself a chance, tried to give myself a chance and see how it felt," Barty said. "Obviously practicing, we've had our restrictions and essentially tried to stay as fresh as possible and not aggravate it in any way, but in a match that's unavoidable at times.

"It got worse today and it was becoming at the stage where it was unsafe. As hard as it is, it... had to be done. Right from the first game, I was battling the pain, and it just became too severe."

The Polish World No.45 is through to the third round of a Grand Slam for the fifth time in her career, where she'll next face No.25 seed Ons Jabeur. Barty ends her clay season with a title in Stuttgart, a runner-up finish in Madrid and a quarterfinal showing in Rome.

"[It's a] completely new injury, and I think something that I've never experienced before, even chatting with my physio, not something she has seen regularly either," Barty said. "So we've been consulting with people all over the world to try and give us some insight into what the best ways to manage it are, to handle it, and I'm confident we do have a plan. It's just that we ran out of time here.

"It's disappointing but not panic stations... We know what's going on. We just need time to manage it to get back on the court as quickly as we can."

After being stretched to three sets in her opening round win over former champion Jelena Ostapenko, Kenin needed much of the first set to familiarize herself with the world No. 203, whom she noted she had "never watched" nor had "no idea how she plays" in previewing the match. 

There was little to separate the two Americans in the opening set after Baptiste retrieved an early break, and each player turned aside further chances that would've seen them take the lead. Baptiste saved four break points at 2-2 and Kenin erased two in the next game, and neither woman again was pressured on serve until Kenin broke at love at 5-5.

The No.4 seed won eight straight points to wrap up a one-set lead, and ran her string of games won to six by opening up a 4-0 lead in the second. Baptiste saved two break points in the fifth game to stop the run, and saved two match points when Kenin served for victory in the eighth game before Kenin eventually wrapped things up.

Two wins in Paris marks just the third time that Kenin has won consecutive matches this year, and first since February's Yarra Valley Classic.

Up next, she'll face another compatriot in No.28 seed Jessica Pegula, who eased to a 6-3, 6-3 win over Tereza Martincova.