Lower back pan, apparently. This means Blah moves on the the semifinals, and is even closer to qualifying for Shanghai. Augh. Someone please beat him.
UPDATE: More on Fed's back:
Federer, meanwhile, pulled out shortly before his quarterfinal against James Blake because of a stiff back, but said he didn't have a serious injury.
Nadal said Federer told him he was hurt as they met in the player's lounge just before he came on to face Davydenko.
"My back has been stiff for the last couple of days and I woke up this morning and it did not respond to the treatment I had last night," Federer said on his Web site. "As a precaution and because I would be unable to play at 100 percent tonight, I have unfortunately had to take the difficult decision not to play."
"Usually the back is something that takes a few days and it's better again," Federer said. "I'm confident and I'm positive that hopefully it's going to get better in the next few days."