Jack Sock played a hilarious prank on Roger Federer during the Match for Africa 5 by serving underarm, which may be one of the only ways to try and beat the 20-time Grand Slam winner.
The 36-year-old took the joke well pointing and laughing at Sock in acknowledgement of his clever trick. The crowd also applauded the American in earnest at the SAP Arena in San Jose, California.
Despite obviously not taking it quite as seriously as a normal tour match, Federer went on to defeat Sock in straight sets, 6-4, 7-6, to demonstrate once again how extraordinary his form is at such a late stage in his career.
The recently re-crowned world number one, won the Australian Open in January to seize his 20th Grand Slam title.
"For me to stand right here as world No. 1 in San Jose is very, very special for me," Federer said.
Federer's "The Match for Africa" exhibition sold in excess of 15,000 tickets to support his foundation that puts investment into education for children in Africa. The charity had raised another $2.5 million by the end of the evening.
Watch Federer take his eye off the ball:
He also lauded Microsoft billionaire owner Bill Gates as a perfect partner for an exhibition doubles match that was also played in California.
"He knows numbers very well. He never makes mistakes on the scores," Federer joked. "I'll do the running and Bill does the thinking."
During one point, Federer called off Gates so he could dominate the rally, "That's mine ... that's mine, too," before Sock lobbed a winner over Gates that Federer couldn't chase down.
"I think I'm good at picking partners," Gates said.
Sock joked before the match in San Jose, "Don't hit it to Roger ... I'm winless against him for my career."
"This match for Africa is something extraordinary," Sock said.
Given how carefully Federer now organises his schedule and the fact he opted out of the clay court part of the season last year, there's every chance the Swiss star could now put his feet up until Wimbledon rolls around.
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