MELBOURNE, AUSTRALIA - - World No. 2 Roger Federer chided on his next nemesis, No.3 Novak Djokovic, expressing doubt of the Serbian’s ability to outnumber him at Aussie Open’s semi-final Thursday.

Federer emphasized that his loss to Djokovic at the 2010 US Open does not guarantee that the Serbian has what it takes to beat him again in this year’s Australian tournament.

To prove his point, Federer enumerated a number of possible reasons why he was defeated by Djokovic in the US Tour.

"I had two match points ... I guess I should have won really. I mean, I was playing good enough to win,” Nine MSN quoted Federer as saying, who said that the US Open battle was a ‘close match’.

The Swiss maestro also claimed that he must have spread himself too thin in the back-to-back game they had at the US Open.

"But I was a bit confused mentally maybe because we played the second session - it was a back-to-back with the Super Saturday (in New York), which I'm not a huge fan of,” Federer added, according to NineMSN.

Federer emphasized that he must have ended the game deliberately to prepare for Spanish superstar and World No.1 Rafael Nadal.

He said, "Maybe I just felt like I have to get out of this match as quick as I could to save energy to play Rafa (Nadal) the next day. I think it ended up hurting me losing the match at the end.”

Federer also discounted Djokovic's Grand Slam singles title which he had won in 2008 Australian Open, making it clear that his game then was affected by some kind of fever, called mononucleosis.

"I had mono," noted Nine MSN the four-time champion said of his defeat in Melbourne in 2008, which marked as his only loss to anyone other than Nadal in six years.

Federer recognizes however that Djokovic is a good player, describing the Serbian ace as confident, offensive and can make a really good opponent. The second seed ended saying he enjoys playing against him for the shot-making they create in court’.