Stefanos Tsitsipas (GRE) returns a shot against David Goffin (BEL) in the Western and Southern tennis open at Lindner Family Tennis Center.
Former world number one and three-time grand slam champion Murray fell at the first hurdle on Monday, upstaged by Lucas Pouille 6-1 1-6 6-4.
Federer and Williams were making their first appearance at the tournament since they each won the title in 2015. "I would be the last person to say I wouldn't want to play with him". "It was a great pleasure to be back".
Playing in only his second tournament with Uniqlo gear, Federer went from his all-white Wimbledon look to the bold, all-black look. Cincinnati was Williams's sixth tournament since giving birth last September. She later clarified that she had been struggling with post-natal emotions.
"You know, this is a long comeback, " she said.
"I'm just going to continue to work hard, and hopefully I'll start winning more matches".
"I was sad not to play here last year, and two years ago there wasn't a chance", Federer said.
'So for the players as well and to attract more people and viewers of a younger audience we have to keep tennis matches dynamic and shorter'.
"It was a tough round for me because I've never beaten her, never even taken a set", said Pliskova.More news: Real Madrid 'must improve in all areas,' says Julen Lopetegui
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Kyrgios, a finalist a year ago in Cincinnati, overcame physical problems to fight off the qualifier Denis Kudla for a 6-7 (2), 7-5, 7-6 (9) victory. "I wish I could play everything, but it's not possible", the 37-year-old added. Then I had an ongoing hip injury.
'In Masters 1000 we have more opportunities to have five-set matches, definitely at the World Finals. You know, there is only so much you can do before you have to get surgery or something like that. "I don't get byes anymore right now".
Swiss Stan Wawrinka dug deep and ultimately prevailed 6-2 4-6 6-3 against twelfth seed Diego Schwartzman in their first career meeting to set up a highly-anticipated battle with Japan's Kei Nishikori. Sock has lost eight straight matches since winning in Rome on May 13.
Unseeded Milos Raonic advanced past Serb Dusan Lajovic 6-3, 6-3 at the combined ATP and WTA event, the last major tune-up prior to the US Open on August 27.
Greece's Maria Sakkari edged 20-year-old Naomi Osaka in a closely contested second-set tiebreak to dispatch the Japanese 6-3 7-6 (8) in their first-round match.
Fifth seed Elina Svitolina outlasted Russian Svetlana Kuznetsova 7-6 (1) 4-6 6-4 in their second-round clash.
Sam Querrey beat ninth-seeded American compatriot John Isner 6-4, 6-7 (5), 7-6 (7/5).
In the day's final game, Canada's Denis Shapovalov defeated British 14th seed Kyle Edmund 6-4, 7-5.