One of the most impressive defensive players I saw this year was Ehire Adrianza, playing shortstop for the Triple-A Fresno Grizzlies in the Pacific Coast League. The Giants promoted him to the major leagues for September, although playing time has been scarce so far.
Signed out of Venezuela in 2006, Adrianza is really impressive to watch on defense. His arm isn't the strongest around, but it is accurate and he has a quick release. He's shown excellent range, especially to his right side, and is reliable as young shortstops go, making just 17 errors in 116 games this year. He is also one of those guys that always seems to be in the middle of a critical play, making his presence known in a positive way. He plays with fluidity and an "alert relaxedness," if that makes any sense.
The thing that has kept him off top prospect lists is offense. A switch-hitter, he has better-than-average speed and is an effective stealer. He also controls the strike zone reasonably well, doesn't strike out that much, will take a walk, and is a good bunter, all positive traits of course. The problem is lack of power: he doesn't have any, and even when he makes solid contact the ball doesn't go very far.
Adrianza somehow hit .310 with a .441 SLG in the Pacific Coast League this year, which tells you a lot about the Pacific Coast League: he hit just .240 with a .312 SLG in the Eastern League before being promoted. Overall, over eight minor league seasons he is a career .248/.335/.344 hitter in 708 games. I'd expect that is about what he'd hit in the majors.
All that said, Adrianza's glove and little ball ability could make him valuable on the bench. The fact that he makes contact and puts in an effort to work the count could give him a chance to surprise us with the bat, eventually. He just turned 24 so he's not especially young, but stranger things have happened.