Federer fires up at umpire over 'bulls**t' call

Roger Federer breezed past Hyeon Chung and into his 30th grand slam final on Friday night, but not before one outburst surprised his passionate fans.

The Swiss maestro was livid with the chair umpire who deemed he had not been hindered by a linesman's incorrect call during his shot - and ruled the point against him.

Federer was reaching out for a pin-point Chung serve when the line judge called the ball 'out'.

However that call was overruled by the chair umpire, who called the ball in, and then deciphered that Federer's return had not been hindered by the initial line call.

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"You're kidding me," an incredulous Federer said.

"It's a bulls*** argument. It was during the shot."

Fed argued that he would have returned the ball to better effect if he hadn't heard the ball was out during his shot.

However the chair umpire stuck to his guns and awarded the point against him.

The incident during the second set, with Federer up three break points in the game, was extremely out of character for the second seed, but reflected his intense competitiveness.

It wasn't the first time Fed has fired up at umpires during this year's Australian Open.

Luckily the controversial call had no bearing on the match, with Federer dominating before the Korean was forced to retire.

The unseeded Korean was a set and 5-2 down against the 19-time grand slam champion when he stunned Melbourne Park and his opponent, by informing the chair umpire he could no longer continue.

Chung was forced to take an injury timeout at 4-1 down in the second set - with trainers attending to a blister complaint on his foot.

The Korean managed to carry on through the pain for the next two games, before pulling the pin at 30-30 when 5-2 down and serving to stay in the second set.

For Federer the 6-1 5-2 passage into his seventh Australian Open final, where he'll come up against Croatian sixth seed Marin Cilic, was tinged with sympathy for his stricken rival.

"Obviously I'm incredibly happy to be in the finals, but not like this," Federer said after the match.

Then in words sure to help lift the spirits of the heartbroken Chung, the 19-time major winner backed the Korean to go on and become one of the sport's next generation of superstars.

"I could tell something was wrong before he took the injury timeout, but he has a great composure," Federer said.

"He is already a great player, but we are talking next level excellence and I think he will achieve that.

"We will see much more of him. Top 10 for sure. The rest we will see.

"I don't want to put too much pressure on him. He has done very well. I can see why he beat the likes of Novak (Djokovic) and Sascha (Zverev) and all the others this week and in the past.

"I think he is going to be a great, great player."

Lleyton Hewitt confirmed in commentary that Chung had been battling the problem throughout the year's first major.

"It's a blisters issue," Hewitt said during commentary.

"He has had some feet issues in the locker room, before every match and on his days off getting a lot of treatment.

"He burns rubber, that is for sure."

Defending champion Federer now has a chance to lift his 20th grand slam singles title and a sixth at Melbourne Park, in Sunday night's decider against Cilic.