UPDATE 2-Tennis-Federer enjoys walkover, Fish ousts Nalbandian

(Adds Fish win)

By Mark Lamport-Stokes

INDIAN WELLS, California, March 21 (Reuters) - World number one Roger Federer reached the last four of the Pacific Life Open without hitting a shot on Friday when his quarter-final opponent German Tommy Haas pulled out with a sinus infection.

Swiss Federer, three times champion at Indian Wells and seeking his first ATP title of the year, will next meet unseeded American Mardy Fish, who scraped past seventh-seeded David Nalbandian of Argentina 6-3 6-7 7-6.

"I deeply regret that I have to withdraw," Haas said in a statement. "I was playing my best tennis of the season and was looking forward to playing Roger this afternoon.

"I am sure the tennis will be incredible this weekend and I look forward to returning again next year."

The 29-year-old, a former world number two whose career has been dogged by injuries, produced an impressive run this week, knocking out sixth-seeded American Andy Roddick and Britain's number 11 seed Andy Murray.

Top seed Federer, who has beaten Haas eight times in 10 career meetings, said: "I am very sorry for Tommy as I was looking forward to another great match with him.

"We have played quite a few times and I know and respect Tommy a lot. I hope he gets better quickly."