Vitters, the club's first-round Draft pick (No. 3 overall) in 2007, has appeared in six games, with three starts. He has two hits in 16 at-bats (.125), one of which was a pinch-hit, two-run double on Aug. 7 against San Diego.
Although the 22-year-old hasn't taken to the Majors quickly, offense is the one thing that has rarely been a question with Vitters. He was a .283 hitter in the Minor Leagues, and he was hitting .304 with 17 home runs an 68 RBIs at Triple-A Iowa before being promoted.
Sveum said he eventually sees Vitters maturing into a player "capable of hitting 20 home runs if he plays every day -- easily 20 home runs.
"His swing should definitely play in the big leagues," Sveum said. "His hands are very live. He's a great fastball hitter, and great fastball hitters usually survive and do well at this level."
Defensively, Vitters is still a work in progress. He's committed one error -- which came Friday on a hard one-hopper that would be a tough play for many players -- but he has also made a couple of impressive stops. Sveum said he already sees improvement when watching Vitters take ground balls, but he's interested to see how that growth translates to game situations.
"That's going to be the evaluation in the next 50 games, however many he plays, the exposure," Sveum said. "This is a lot of evaluation, and we'll see where we're at as soon as he's getting more exposed with game-time ground balls and everything."