Jackson is one of the top prospects in the Cubs' system. He is batting .259 in 41 games at Double-A Tennessee this season, although he had to miss time because of a finger injury. He was on the disabled list from May 12-29, and in nine games since returning from the DL, he's 5-for-35.
The speedy outfielder, who has primarily played center, has 13 stolen bases and has been caught stealing three times. He has seven doubles, three triples, six homers and 23 RBIs. Jackson, batting .295 when injured, could be called up in September. The Cubs are going with a youth movement because of injuries to key players but won't rush Jackson.
A highly touted right-handed pitcher, Trey McNutt was invited to Spring Training but didn't get much action because of injuries. He missed time earlier this season because of a blister and is currently on the disabled list with bruised ribs suffered in a collision on May 28. McNutt, a 32nd-round pick in the 2009 Draft, tried to pitch despite the soreness on June 2 and had to come out after two innings.
In nine starts with Tennessee, he's 1-2 with a 2.70 ERA, giving up 11 earned runs over 36 2/3 innings. He'll most likely stay in the Minors this season.
Chris Carpenter, a third-round pick in 2008, began the season with Triple-A Iowa and was 2-1 with a 6.41 ERA in 13 games, all relief appearances, after spending his previous three seasons in the Minor Leagues as a starter. But he walked 17 and gave up 20 hits over 19 2/3 innings, and was sent to Double-A Tennessee in mid-May. In eight games with the Smokies, he's 1-1 with one save and a 5.23 ERA.
The Cubs' No. 1 Draft pick last year, Hayden Simpson, began this season at Class A Peoria. He is 1-3 with a 4.96 ERA in 12 starts. He's struck out seven twice, including his first start April 7 in 3 2/3 innings. Simpson is a little behind after not being able to play following last year's Draft because he came down with mononucleosis.
Josh Vitters, the Cubs' No. 1 pick in the 2007 Draft, is batting .274 in 53 games with five homers, 12 doubles and 28 RBIs. He's been slowed by injuries, including a fractured finger on his left hand last year.
Vitters played well in the Arizona Fall League last October, and coaches who have worked with him in the Cubs system have noticed a more mature individual. He was selected out of high school and is just 21. If all goes well, he could get a September callup.
Jay Jackson, a ninth-round pick in 2008, is 2-5 with a 6.15 ERA in nine starts at Triple-A Iowa. A Spring Training invitee, he has 19 strikeouts over 45 1/3 innings. The right-hander was 11-8 with a 4.63 ERA in 32 games last season at Iowa. Jackson had a nightmarish May, when he was 0-4 with a 10.38 ERA, which has inflated his numbers. In two June starts, he's 1-1 with a 2.25 ERA. Obviously, he needs to show more consistency.
Rafael Dolis is 3-3 with a 2.45 ERA and five saves at Double-A Tennessee. He made four starts, but that was in his first four appearances. He was then shifted to the bullpen. Dolis has a 2.25 ERA in 15 games in relief, fanning 11 in 20 innings. He's also walked 11 and needs to improve on command. He was bumped up to Tennessee last season and still is at least one year away.
The only time Matt Szczur has missed this season is to attend graduation ceremonies at Villanova. A fifth-round pick in 2010, the outfielder is batting .331 in nine games, with three homers, 11 doubles and 16 RBIs. He's also stolen 14 bases. On June 2, the Chiefs' leadoff man was 4-for-6 and scored three runs. Szczur needs more seasoning but may be moved up a level at some point this year.
An eighth-round pick in 2009, Robert Whitenack went 3-0 with a 1.17 ERA in four starts at Class A Daytona -- including a 12-strikeout game on April 12 -- and was moved up to Tennessee. He went 4-0 with a 2.39 ERA in seven starts there, striking out 22 over 37 2/3 innings. But the right-hander felt some discomfort in his arm, and on Tuesday underwent Tommy John surgery on his elbow. The Cubs were considering moving him up again before the injury. Now, he'll spend the offseason rehabbing.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter@CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.