Roger Federer of Switzerland leaves the court after his upset loss against Britian's Andy Murray. Federer lost, 6-7, 6-3, 6-4, to Murray on Monday during the first round of the Dubai Tennis Championships.

Dubai, United Arab Emirates ? Roger Federer is on a losing streak for the second time in four months.

The top-ranked Federer, who won three Grand Slam titles last year but has struggled since the U.S. Open, lost to Andy Murray, 6-7 (6), 6-3, 6-4, on Monday in the first round of the Dubai Tennis Championships.

Federer was playing for the first time since losing to Novak Djokovic in the Australian Open semifinals Jan. 25. He said he felt rusty.

Playing Murray, who is ranked 11th in the world and beat Federer at the Cincinnati Masters two years ago, in the first round didn’t make things any easier on Federer.

Murray now leads Federer, 2-1, in his career.

Federer, who won the Dubai tournament four times in the last five years, had not lost in the first round of a tournament since his defeat to Dominik Hrbaty in the 2004 Cincinnati Masters.

“He’s the best player in the world, there’s no question,” Murray said.