Roger Federer made a successful return to the Western & Southern Open on Tuesday.
The day wasn't so great for Serena Williams.
Federer advanced to the third round with a 6-4, 6-4 victory against Peter Gojowczyk, and Williams was eliminated by eighth-seeded Petra Kvitova in a 6-3, 2-6, 6-3 second-round loss.
Federer and Williams were making their first appearance at the tournament since they each won the title in 2015. Williams opened with a straight-set victory against Daria Gavrilova.
After a first-round bye, Federer extended his Cincinnati winning streak to 11 matches since losing to Rafael Nadal in the 2013 quarterfinals.
"It doesn't feel like I have been away for so long here from Cincinnati," Federer said. "I guess the wheel keeps turning. It's not like I missed two years of tennis. It was a great pleasure to be back."
The second-seeded Federer, refreshed from a month off after losing in the Wimbledon quarterfinals, became the tournament favorite when Nadal withdrew on Sunday night.
Williams also was knocked out in her last tournament at San Jose two weeks ago after reaching the Wimbledon final. Cincinnati was her fifth tournament since she had a baby last September. She has dealt with blood clots and recently said she has been struggling with postpartum emotions.
"You know, this is a long comeback," she said. "I just began. I just started — definitely at the very, very beginning. I'm getting there, and I'm going to just continue to work hard, and hopefully, I'll start winning more matches."
Karolina Pliskova and Nick Kyrgios also advanced Tuesday in early tournament action.
Pliskova moved into the second round by snapping a seven-match losing streak against Agnieszka Radwanska with a 6-3, 6-3 win.
"It means a lot because it was against her, and, like, you know, I never beat her," Pliskova said. "We played so many times. I think I always played her at her best level the matches before, so it was always tough."
Kyrgios, a finalist last year in Cincinnati, overcame physical problems to fight off qualifier Denis Kudla for a 6-7 (2), 7-5, 7-6 (9) victory.
"This year has been tough," Kyrgios said. "I started the year very well. Then, obviously, I hurt my elbow. Then I had an ongoing hip injury. We have been definitely thinking about the options with my hip. You know, there is only so much you can do before you have to, you know, I guess, get surgery or something like that. You know, right now I'm just managing it."
No. 11 seed David Goffin advanced with a 7-5, 6-3 win over Stefanos Tsitsipas, and Leonardo Mayer became the first player to reach the third round on the men's side with a 7-6 (7), 6-4 victory over 16th-seeded Lucas Pouille.
Denis Shapovalov also reached the third round with an upset, knocking off 14th-seeded Kyle Edmund, 6-4, 7-5.
Australian Open semifinalist Hyeon Chung won the last five games to beat Jack Sock 2-6, 6-1, 6-2. Sock has lost eight straight matches since winning in Rome on May 13.
Two-time Cincinnati semifinalist Milos Raonic advanced with a 6-3, 6-3 win over qualifier Dusan Lajovic. Robin Haase also made it to the second round, defeating Filip Krajinovic 4-6, 6-2, 6-3.
Fifth-seeded Elina Svitolina was tested by wild card Svetlana Kuznetsova before reaching the third round with a gritty 7-6 (1), 4-6, 6-4 win. Sixth-seeded Caroline Garcia also reached the third round with a 6-4, 6-5 win over wild card Victoria Azarenka, but 12th-seeded Daria Kasatkina suffered a first-round upset at the hands of qualifier Petra Martic, 4-6, 6-4, 6-3.
Elise Mertens scored a 6-4, 6-2 first-round win over Magdalena Rybarikova. Ashleigh Barty stopped wild card Marketa Vondrousova 6-3, 7-5.
Maria Sakkari upset Indian Wells champion Naomi Osaka 6-3, 7-6 (8). Ekaterina Makarova cruised past qualifier Ana Bogdan 6-3, 6-2.