A's manager Bob Melvin said closer Grant Balfour will undergo knee surgery Wednesday to repair a torn meniscus. He is expected to miss 4-6 weeks, but Balfour could be ready for the start of the season. "I feel good about getting it done now. It will allow me to get ready for Game 1 of the season," Balfour said in a statement. "I knew the way I was feeling I wouldn't have been able to pitch through it all season long." If Balfour misses the start of the season, Ryan Cook and Sean Doolittle would be options to close games.