The outfielder, who showed promise in 2010 when he hit 20 homers, was batting .151 with six homers this season heading into Wednesday's final game. Colvin will spend the offseason in the Phoenix area, working out at the Cubs' facility.
"He's going to concentrate on getting stronger," Cubs manager Mike Quade said. "He's got decent strength, and he's going to get stronger. He's got bat speed, and can hit the ball out of the ballpark. Those are givens. But you've got to be able to put the barrel on the ball consistently. That's discipline, improvement, that's continuing to work on your swing plane -- that's all sorts of things that I don't think were prominent when he first got started."
The question now is whether Colvin can make the adjustments to succeed in the big leagues.
"The ball's in his court," Quade said.