The three-time AL MVP suffered a calf strain on May 17 and hasn't returned to the lineup since. The original prognosis was six to eight weeks of rehabilitation, but the injury was worse than originally thought.
Trout was trying to get back this season, but recently made the decision that he was done this year.
The 30-year-old outfielder said he's healthy and should have a normal offseason in New Jersey.
"It's been tough for me, but now looking back and learning from everything, this was the biggest injury of my career," Trout said.
"It came down to we were trying everything the last month and a half to get back out there. My calf and my body weren't cooperating. It was frustrating. I took a week, 2 1/2 weeks off and I feel almost 100%."
Trout hit .333 with 8 home runs, 18 RBI and a 1.090 OPS in 36 games this season.