DENVER -- After dominating Double-A competition during four rehab starts, right-hander Alex White will make his Rockies debut on Tuesday against the Astros.

Rockies manager Jim Tracy announced on Saturday that White will take the rotation spot of Jason Hammel, who will move to the bullpen on the heels of a 1-2 record with a 9.33 ERA in four August starts.

White's start will give fans their first chance to see one of the four players involved in the deal that sent former Rockies ace Ubaldo Jimenez to Cleveland just before the non-waiver Trade Deadline.

"We want to see him," Tracy said of White.

Tracy said he hasn't set a pitch count for White's start on Tuesday, but added that he'd be monitoring the hard-throwing righty closely to see how he handles "the different dynamics" of pitching at high altitude. The Rockies' skipper said he's told White not to feel like he has to make huge statement in his first Rockies start.

"There's going to be a patience level involved with this young man, and I wanted him to hear that from me," Tracy said.

White has had his patience tested this season, as he's missed much of the campaign with a torn pulley tendon in his right middle finger. But he showed little rust during his rehab assignment with Double-A Tulsa, going 1-1 with a 1.65 ERA over four starts (16 1/3 innings). The right-hander made his Major League debut with Cleveland this season, where he was 1-0 with a 3.60 ERA over three starts.

"I'm very excited," White said. "It's a long time coming. I feel like I've been on the DL now for three months, and it's just a good feeling to be back healthy and be helping this team."

White was dominating in his most recent rehab start on Thursday, when he threw 7 1/3 scoreless innings of three-hit ball. As that evidence suggests, White's health concerns are in the rearview mirror.

"I feel great," White said. "The biggest concern with the rehab was getting the arm back in shape, and we've done that. My arm feels very good. Getting back to 100 percent, we're right at that."

Right-hander Aaron Cook will have his next start moved to Wednesday.

Tracy moves Hammel to bullpen

DENVER -- Rockies right-hander Jason Hammel will have to solve the mystery of his inconsistency from the bullpen.

Hammel has shown a dominating arsenal at times for the Rockies this season, but an inability to string together strong outings led manager Jim Tracy to remove the right-hander from the rotation on Saturday. Right-hander Alex White will take Hammel's spot and make his Rockies debut on Tuesday against the Astros.

"It's very disappointing," Hammel said. "Obviously, I know I'm better than what I've been doing. This is a long time coming. When you're trying to put together a successful team on the field, you can't have a guy that's a question mark every time out."

Tracy said Hammel, who is 7-12 with a 5.24 ERA as a starter, will move to bullpen in a long-relief role, where he'll pitch "innings that make sense to give him an opportunity to straighten things out."

Hammel's inconsistency was exhibited in his past two starts. In the first, against the Cardinals on Aug. 13, he delivered a win by tossing 6 1/3 innings of five-hit, one-run ball. But on Friday, he lasted only three innings after giving up six runs.

"His start five days ago against the Cardinals versus the one we saw [on Friday] night -- it's at completely opposite ends of the spectrum," Tracy said. "If you're trying to create some momentum and gain some consistency as a ballclub, it's very, very difficult to vacillate back and forth like that."

Hammel, who said he dealt with a dead arm at the end of the 2010 season, said he's "fine" physically.

"It's definitely between the ears," Hammel said. "I've just got to find some way to unlock whatever it is that helps guys click, because sometimes it does and sometimes it doesn't. I've got to find a way to make sure it's there every time."

Hammel said he was given the option of trying to work through his struggles as a starter in the Minor Leagues. But with the season nearing an end, the right-hander thinks he'll be better served to work on his craft out of the bullpen.

"I'm not giving up on starting," Hammel said. "It's what I've always done. It's just very disappointing that it's come to this, but you have to do what's best for the team right now, and I can't keep killing the bullpen."

Lindstrom, Street on pace to return on time

DENVER -- Rockies relievers Matt Lindstrom and Huston Street each threw bullpen sessions on Saturday, and each will begin rehab assignments on Monday.

Lindstrom has been on the 15-day disabled list since Aug. 10 with a nerve injury in his right arm, and Street has been shelved sine Aug. 12 with a right triceps strain. Both are expected to pitch on Monday and Wednesday. If those outings go well, each player could return to the lineup on the day he is eligible to come off the DL.

In other injury news, outfielder Ryan Spilborghs is set to begin a rehab assignment on Saturday night at Triple-A Colorado Springs. Spilborghs has been on the DL since Aug. 6 with plantar fasciitis in his right foot.