Wimbledon’s famed grass courts are under the microscope after a stack of accidents with big stars in the first two days of the grand slam.

Mercurial Australian Nick Kyrgios also had a moan about the courts in a signature tantrum in his first-round encounter with talented young Frenchman Ugo Humbert.

“Guys, for you watching at home, it should be fast in here. It should be fast, that’s grasscourt tennis,” Kyrgios muttered.

“They’ve made it slow. This isn’t grass anymore. This is slow. Slow.

“Try watering it. Make it a grass court again, thanks.”

The clash was suspended at two sets apiece five minutes before 11pm local time on Tuesday because of a London curfew. There were boos and jeers from the crowd as the tournament supervisor came onto court to tell the players to leave.

Kyrgios and Humbert were locked at 3-all in the deciding set when officials called time out on a rain-marred day two of the Championships.

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Earlier, Roger Federer admitted he got lucky after Adrian Mannarino was forced to retire from their first-round match at Wimbledon with a knee injury.

Eight-time champion Federer advanced to the second round on Tuesday when his French opponent retired with a knee injury after slipping on court.

The Centre Court match was poised at 6-4 6-7 (3-7) 3-6 6-2 with Federer forcing a fifth set before Mannarino, on his 33rd birthday, decided he could not continue.

“It’s awful,” sixth-seeded Federer said in his on-court interview.

“It shows that one shot can change the outcome of a match, a season, a career.

“He could have won the match at the end.

“Obviously, he was the better player, so I definitely got a bit lucky.”

World No.1 Novak Djokovic said he did not recall “falling this many times on court” after several tumbles in his opener against Britain’s Jack Draper on Monday, while Andy Murray said it was “extremely slippy out there”.

A “heartbroken” Serena Williams was also forced to retire after slipping during the fifth game against Aliaksandra Sasnovich.

The American returned after a 10-minute delay and hit a handful of winners, but the pain in her right leg appeared too severe and she had to quit in tears.

“I was heartbroken to have to withdraw today after injuring my right leg. My love and gratitude are with the fans and the team who make being on Centre Court so meaningful,” she said in a statement later.

“Feeling the extraordinary warmth and support of the crowd today when I walked on – and off – the court meant the world to me.”

Federer, who learned of Williams’ injury during his news conference, said the court felt drier during the day.

“I feel for a lot of players – it’s super key to get through those first two rounds because the grass is more slippery, it is more soft,” he said.

“As the tournament progresses, usually it gets harder and easier to move on.”

And it wasn’t only Centre Court where players had problems with their footing.

On court two, Coco Gauff was unable to stay on her feet on numerous occasions as she managed to get past Francesca Jones 7-5 6-4.

“I think everybody saw me slipping and sliding,” American teen Gauff said.

The All England Club in a statement said the wettest two opening days of Wimbledon “in almost a decade” indirectly led to “additional moisture” on the grass at centre court while the retractable roof had been closed for long periods.

Kyrgios, who is playing his first tournament outside Australia in 18 months, will resume his delayed Wimbledon clash on Wednesday (local time).

-with AAP