It seems like Jennings has been around for a while. He's 24 and has been on top prospect lists for years as well as spent some time with the big club last season. However, injuries have held him back a bit, both to his wrist and shoulder last season and to his finger this season. Through it all, Jennings has still produced. Last season, a wrist injury caused a bit of a power outage, but he still managed to hit .278/.362 with 37 stolen bases in 485 plate appearances. The power/speed numbers have returned this season as Jennings has 12 homers in 391 plate appearances to go along with 17 stolen bases.
One of Jennings's best attributes is his plate discipline. He doesn't chase outside the strike-zone too often and draws a good amount of walks, which make him an instant threat in OBP leagues (.370 OBP at triple-A this season). In the long run, that discipline should help him hit for AVG/OBP at the big-league level, but what about the present?
The 2011 season started slow for Jennings, as he hit .258 and .275 in April and May respectively, but hit .296 in June and has been hot in the month of July, putting up a slash line of .283/.426/.510 with a line drive rate of 27 percent (stats according to FirstInning.com). If he can carry that hot-streak to the big-leagues, he can certainly put up some numbers for fantasy owners right away.
The problem is trusting a young player and we've seen a lot of rookies struggle early upon their call-up. That being said, most prospects that have been called up are at least a couple of years younger than Jennings, who has almost 1000 plate appearances at triple-A. While it would be tough to expect a ton of production from Jennings, he has the power/speed potential that could be a game-changer for many fantasy GM's. Of course you add him in AL-only and deep mixed, but, depending on who you drop to get him, Jennings can be added in just about any format.
Eyeball ROS projection: .277/.355/.446 with 5 HR and 12 SB.