"I'm kind of a glass-half-full guy, so I'm looking at it as, if there was ever a time to have it done, it would be now," manager Bob Melvin said.
Balfour, 35, who is entering his third season with Oakland, echoed those sentiments in a statement released by the team.
"I feel good about getting it done now," Balfour said. "It will allow me to get ready for Game 1 of the season. I knew the way I was feeling I wouldn't have been able to pitch through it all season long."
Melvin said Balfour felt some knee tenderness toward the end of last season, but went about his normal offseason routine without any pain before experiencing some on Wednesday prior to his scheduled bullpen session. Balfour proceeded with his side session, after which the A's opted to be proactive and send him for an MRI that revealed the tear.
The operation was performed by local orthopedist Dr. Douglas Freedberg, who also operated on Scott Sizemore last spring, when the A's infielder suffered a torn ACL on the first day of workouts.
"He's a grinder," Melvin said of Balfour, "and he feels like he'll be able to rehab very quickly. He keeps himself in great shape."
"He'll be ready," reliever Ryan Cook said. "I fully believe he will be. I don't expect him not to be."
In the meantime, the A's are more than comfortable with their bountiful bullpen depth. Should Balfour end up missing time during the regular season, Cook and Sean Doolittle are options to close.
"Those are the obvious choices, but we'll see how it goes," Melvin said. "Again, depth comes into play. We're not ruling Grant out to start the season, but this is the reason you accumulate as many guys as you can."
Balfour compiled 24 saves in 2012, posting a 2.53 ERA and 0.92 WHIP in a career-high 74 2/3 innings spanning 75 games. He also pitched 1 2/3 innings during the postseason, making for a large workload in total. That was why the A's planned to bring the veteran along slowly in camp, and they're now assured his arm will get the needed rest while he rehabs his knee.
"That might be a little underlying positive," Melvin said. "We were going to take it easy on him from the start."