A team official said Arrieta is expected to be full-go for spring training, which is why it made sense for the pitcher to undergo surgery now instead of waiting until after the season or relying on cortisone injections and treatments.
Arrieta will return to Baltimore before the season ends.
Meanwhile, Tigers No. 9 hitter Wilson Betemit hit a two-run homer off Alfredo Simon in the top of the fourth inning, giving Detroit a 4-2 lead and further slowing the pace of this game.
Arrieta might be full-go by the time we reach the seventh-inning stretch.
Simon has allowed 10 hits, and we're still waiting for him to record the first out in the fourth inning. Troy Patton is warming in the bullpen and should be coming in shortly.
Instant update: Nick Markakis caught Magglio Ordonez's fly ball in right field and threw out Austin Jackson at the plate for his 11th outfield assist. Two quick outs for Simon, who badly needed them.
Update II: Tigers pitcher Al Alburquerque suffered a concussion after being hit in the head by a Robert Andino line drive in batting practice. He'll be held overnight at University of Maryland Hospital.