Miami - Roger Federer withdrew from the ATP and WTA Miami Open on Friday with a stomach illness only hours before his scheduled return from a two-month layoff following left knee surgery.
The 34-year-old Swiss star, winner of a men's record 17 Grand Slam singles titles but none since Wimbledon in 2012, was replaced by lucky loser Horacio Zeballos for a second-round match against Argentine compatriot Juan Martin Del Potro.
"Sorry for him, sorry for the tournament, sorry for the fans," said long-time Federer rival Rafael Nadal when told the news.
"It's good it's a stomach problem and not the knee, but it's the same for this tournament."
Federer won at Miami in 2005 and 2006 but has not reached the final since. This marks the third time in four years he has missed the event.
World number three Federer, who appeared well Thursday in speaking with reporters, has not played since losing to eventual champion Novak Djokovic in the Australian Open semi-finals two months ago.
The next morning, Federer suffered a torn meniscus making a simple move as he was preparing to bathe his children.
"I turned. I turned back. I felt a click in my knee," Federer said on Thursday.
"It was a very simple movement, one I've done a million times. I'm glad it didn't happen on a tennis court, where I could have strained it more."
Federer said he had not expected to be ready in time to play at Miami and warned that if he felt a knee problem he would not take part, but ATP officials confirmed he was suffering from a gastric virus and did not withdraw over any issue with the knee.
"Expectations are really low, which is nice for a change," Federer said Thursday. "I didn't expect myself to be back here quite honestly after the surgery."
Meanwhile, reigning Australian Open champion Angelique Kerber and Czech seventh seed Tomas Berdych both advanced to the third round.
Kerber, the second seed from Germany, downed Czech Barbora Strycova 6-1, 6-1 while Berdych, the Miami runner-up in 2010 when he also reached his lone Grand Slam final at Wimbledon, won by walkover when American Rajeev Ram withdrew due to illness.
Berdych, who like all seeds had a first-round bye, will not take the court until Sunday, when he faces either American Steve Johnson or Germany's Alexander Zverev.
Kerber raced through the first set in 32 minutes, firing 10 winners and aided by 15 unforced errors from Strycova, and broke three times in the second set, the last to love to end matters after only 63 minutes.
"I was trying to be focused, just playing my game," Kerber said. "First matches can be tricky."
Next up for Kerber, whose best Miami showing was a 2014 quarter-final run, is 108th-ranked Dutch qualifier Kiki Bertens, who dispatched Russian 25th seed Anastasia Pavlyuchenkova 6-1, 4-6, 6-1.
World number one Djokovic, trying to complete an Indian Wells-Miami back-to-back double for the third year in a row, opens his quest for a sixth career Miami crown later against Britain's 87th-ranked Kyle Edmund.
The Serbian top seed won his 11th major singles title at the Australian Open in January.
Scores on Friday from the fourth day of the ATP and WTA Miami Open (x denotes seeded player):
Tomas Berdych (CZE x7) bt Rajeev Ram (USA), walkover, illness
Marin Cilic (CRO x11) bt Dusan Lajovic (SRB) 6-4, 6-1
Dominic Thiem (AUT x14) bt Sam Groth (AUS) 7-5, 6-2
Lucas Pouille (FRA) bt Guillermo Garcia-Lopez (ESP x32) 6-2, 6-4
Yoshihito Nishioka (JPN) bt Feliciano Lopez (ESP x21) 6-4, 6-4
Angelique Kerber (GER x2) bt Barbora Strycova (CZE) 6-1, 6-1
Kiki Bertens (NED) bt Anastasia Pavlyuchenkova (RUS x25) 6-1, 4-6, 6-1
Timea Babos (HUN) bt Karolina Pliskova (CZE x17) 5-7, 6-2, 7-6 (7/0)
Magda Linette (POL) bt Jelena Jankovic (SRB x18) 1-0, retired, right shoulder injury
Naomi Osaka (JPN) bt Sara Errani (ITA x14) 6-1, 6-3
Nicole Gibbs (USA) bt Kristina Mladenovic (FRA x27) 6-2, 6-4