Novak Djokovic and Roger Federer played doubles together for the first time on Saturday but don’t be surprised if they decide never to pair up again.

The two singles Grand Slam champions were playing in the Laver Cup exhibition tournament for Team Europe, who had already taken a 3-0 lead over Team World. Federer and Djokovic were taking on Kevin Anderson and Jack Sock when the Serbian did something, well, embarrassing.

Playing from the baseline, the US Open champion hit one of his booming cross-court forehands...right into the lower back of Federer, who was near the net.

Federer wasn’t hurt by the shot and laughed it off, while Djokovic covered his face with his hands in embarrassment.

“That’s why we don’t play doubles, right?” Federer said to Djokovic during a break between games. “Oh my god, I think my heart stopped for like three seconds,” the Serbian replied.

Federer and Djokovic went on to lose the match after a tiebreaker 6-7, 6-3, 10-6.

This is the second instalment of the Laver Cup which has been dubbed the Ryder Cup of tennis – although it lacks the tradition of golf’s premier team event.

The exhibition is taking place on US soil for the first time and features 12 of the world’s top players squaring off against each other in a three-day showcase which wraps up Sunday in Chicago.

The format calls for shorter matches. If the players split sets, they go straight to a 10-point tiebreaker.