Former rival pokes fun at Federer's rare air ball

Lleyton Hewitt has had a good old chuckle at his former nemesis Roger Federer after the Swiss great produced a rare fresh airy on Friday night.

Federer was demolishing South Korean youngster Hyeon Chung in their semi-final on Rod Laver Arena when the mishit went down.

The world No.2's forehand was on song as he took out the first set 6-1 in 33 minutes, but it was off in one particular point in the final game when it flew right by his racquet.

"Just to make everybody feel a little bit better, there's a swing and a miss!" said former Australian doubles champion Todd Woodbridge.

But the former world No.1 Hewitt wasn't so kind to the man who defeated him in the 2004 US Open final.

"We better have another look at this," laughed the Aussie great.

"Because it doesn't happen too often!"

Federer, 36, had produced dominant tennis against a 21-year-old opponent who had reached the semi-final with stunning wins over Alexander Zverev and Novak Djokovic.

Coming to the end of his biggest tournament since becoming a professional, Chung called for the trainer midway through the second set.

It was speculated that he was suffering from blisters on the bottom of his feet.