Gibson underwent an appendectomy Wednesday and will miss the next 3-6 weeks, the team announced Thursday.
Gibson had been practicing with the Ducks during training camp but didn't get into a preseason contest. He had a 13-27-2 record, 3.54 GAA and .888 save percentage in 46 games last season. Lukas Dostal might have gotten the start Opening Night regardless of Gibson's availability, but Dostal will be leaned on heavily while Gibson is out. While the 31-year-old Gibson is recovering, Oscar Dansk will likely serve as the No. 2 goaltender.