Oakland's first injury of the spring is not a major one, but it is to a key contributor: Closer Grant Balfour will miss four to six weeks with a meniscus tear in his right knee. Balfour could well be ready for Opening Day - he had arthroscopic surgery Wednesday, and the recovery estimate includes rehab time. So if he is back in four weeks, he would be on the mound well before the end of spring training, and, as a reliever, he does not need to build up innings. Balfour's teammates believe the fiery Australian will return even sooner, which would not be uncommon with arthroscopic surgery. NFL players have been back in games in mere weeks. "I'm not even worried about it, to be honest," reliever Jerry Blevins said. "He's a guy who works hard, and if he's true to form, he'll be back very quickly." "He'll definitely be back in day one," left-hander Travis Blackley said. "The only thing he'll need is some fine-tuning, finding his release points. And he'll just lock it in, like he always does." Balfour said in a statement released by the team that he felt knee soreness near the end of last season, but it went away during the winter, even during his workouts. Balfour was able to throw a full side session Wednesday, but the knee became sore and the training staff sent him for a precautionary MRI exam, which showed the small tear. Dr. Doug Freedberg, who repaired Scott Sizemore's torn anterior cruciate ligament last spring, performed the arthroscopic surgery. "I feel good about getting it done now," Balfour said. "It will allow me to get ready for Game One of the season. I knew the way I was feeling I wouldn't have been able to pitch through it all season." Read more: http://www.sfgate.com/athletics/article/Grant-Balfour-knee-out-4-6-weeks-4280190.php#ixzz2KzEiA941