The most impressive thing about Grant Balfour's rebound from Thursday's surgery wasn't the fact that he got to the A's Phoenix Municipal Stadium clubhouse at 7 a.m. as usual Friday. It wasn't that he started right in on his rehab work just 18 hours after surgery to repair a right knee meniscus tear. It was that he was able to stand up for a 10-minute interview on his newly reconstructed knee without any obvious pain or discomfort. The Oakland closer is one tough dude. And that toughness is one reason the A's are hopeful that he will meet or beat the expectations of his being ready to pitch in four to six weeks, which would have him ready to go for opening day.