Cubs rotation deep despite the lack of true ace

While none of those top three pitchers in the Chicago rotation can yet be considered an ace, the Cubs should be able to make up for the lack of a true No. 1 with their potential depth.

"One way or another, we're going to have five pretty good starters to start the season," manager Dale Sveum said. "You have three guys that can go out there with no-hitter type stuff."

There are several options to fill in the gaps after that, including three more newcomers like Jackson.

Scott Feldman won 17 games for Texas four years ago, Carlos Villanueva has been a starter and reliever, and Scott Baker has a 63-48 career record, though he will miss the start of the season after elbow surgery that forced him to miss all of 2012 for Minnesota.

"I'm excited to watch those guys throw," Samardzija said. "I think we've got pretty good chemistry here. We're all going to help each out, really bringing them into the mix with us. But if we can stay together as a group, all five, then it's going to work better for everybody."

And don't forget 26-year-old left-hander Travis Wood, who joined the rotation last May and stayed there the rest of the season — though he's got to win a spot this spring. Wood's 156 innings and 26 starts were surpassed only by Samardzija for the Cubs.

"All great pitchers, and whenever we do get our final five, I think it's going to be a tough rotation," Wood said. "I think the potential is as high as it can be."

Garza (15-17, 3.52 ERA in 49 starts for the Cubs the past two years) missed the final two months last season because of a stress reaction in his right elbow. He then sustained a pulled muscle in his left side only a few days into spring training.

While Garza was set Thursday to resume a throwing program, he indicated that he would proceed cautiously. He's not planning to rush things this spring, hoping that will help prevent any more issues into the season.

"If I try to rush and be ready April 1, I might be re-injured in June, and be out," he said. "If I take my time, maybe I'm pitching April 15 through October, maybe November."

After Ryan Dempster and Paul Maholm were traded in late July, Samardzija became the workhorse starter in a rotation suddenly filled mostly with Triple-A hurlers.