PARIS - Roger Federer lost an argument. His tennis was more persuasive.
Miffed by a line call in his first match as French Open defending champion, Federer quickly regrouped to win the opening set two points later, then went on to beat Peter Luczak, 6-4, 6-1, 6-2, on Monday.
Top-ranked Serena Williams encountered a stressful situation herself late in the first set, when she erased three break points before going on to beat Stefanie Voegele, 7-6 (2), 6-2.
The top-ranked Federer committed only 11 unforced errors, lost just 14 of 64 points on his serve and faced only one break point.
"It's always important coming back as defending champion trying to get off to a good start," he said. "It was like a perfect match to get off the French Open campaign, really."
This is only the second time in nine years that Federer arrived in Paris without a title during the clay season. But the 16-time Grand Slam champion showed no signs of vulnerability against Luczak, an Australian who fell to 0-4 at the French Open.
On match point, Federer leaned into a backhand and pulled it at an improbable angle for one last winner, prompting a final "Ahhhhh" from the crowd.
Williams, who had lost two of her last three matches heading to Roland Garros, used her serve and aggressive returns to pull out the first set. She hit three service winners late in the tiebreaker and finished with 10 aces.
Williams said she was displeased with her performance but declined to discuss specifics.
"I definitely didn't feel good about it," she said. "At least I won. I think I'm still in the tournament; that's what matters."
The 12-time Grand Slam champion seeks her second French Open title and her first since 2002.
No. 3-seeded Novak Djokovic, a two-time semifinalist, beat Evgeny Korolev, 6-1, 3-6, 6-1, 6-3. No. 4 Andy Murray rallied from two sets down to beat Richard Gasquet, 4-6, 6-7 (5), 6-4, 6-2, 6-1.
Americans Taylor Dent and John Isner also advanced. The unseeded Dent won a match at Roland Garros for the first time in his 12-year career, beating Nicolas Lapentti, 6-3, 6-4, 7-6 (3).
"Better late than never, right?" Dent said. "There's nothing more that Americans love than to come over here and win matches. We always have that label, like, 'Oh, you're American. First round, see you later.' So I think we get a lot of pride from winning matches here."
Another American, Michael Yani, lost a 71-game match that equaled the longest at the tournament since the tiebreaker was introduced in 1973. Lukas Lacko beat Yani, 4-6, 7-6 (5), 7-6 (4), 6-7 (5), 12-10. The match resumed at 8-all Monday after being suspended overnight because of darkness.