'Worst in history': Roger Federer ridiculed over baffling Wimbledon moment

Roger Federer might be into his 31st Grand Slam final after moving past longtime rival Rafael Nadal at Wimbledon, but many still claim the Swiss maestro is the worst challenger in history after a bizarre moment in the semi.

The semi-final was hanging in the balance with Federer only a few points away from winning when the 20-time Grand Slam champion cost himself the point.

Nadal, serving 3-5 down, hit a serve which Federer returned with a clean winner.

But thinking his shot was going out, Federer challenged the serve.

Roger Federer in action against Rafa Nadal at Wimbledon. (Photo by Clive Brunskill/Getty Images)

The look on Federer’s face after the challenge said it all with the ball clearly in.

The incorrect challenge handed the point to Nadal and he went on to hold the game to force Federer to serve for the match.

Fortunately for Federer, he was able to hold his nerves and serve out the match.

Fans on social media couldn’t quite believe the mistake in such a crucial game.

Federer ‘exhausted’ after Rafa epic

Federer reigned supreme in the semi-final showdown with Nadal claiming a 7-6 (7-3) 1-6 6-3 6-4 win in another classic on Friday.

Roger Federer has exacted sweet revenge over Rafael Nadal to sweep into a record 12th Wimbledon final with an enthralling four-set triumph over the mighty Spaniard.

Echoes of 2008 reverberated around the All England Club as Federer and Nadal wound back the clock in their much-anticipated first Wimbledon match-up in 11 years.

But unlike Nadal's five-set victory in that epic encounter more than a decade ago, a match dubbed the greatest of all time, Federer reigned 7-6 (7-3) 1-6 6-3 6-4 in another classic on Friday to set up a blockbuster final with world No.1 Novak Djokovic.

"I'm exhausted. It was tough at the end. Rafa played some unbelievable shots to stay in the match," Federer said.

"The match a very high level and I enjoyed it. The crowd was amazing. Battles with Rafa are always very special.

"It was tough. I had spells where I really was serving very well. I thought probably the biggest points in the match went my way.