ST. LOUIS -- After throwing well in a simulated game Wednesday at Busch Stadium, Rockies lefty Chris Rusin will soon begin a Minor League rehab assignment at Triple-A Albuquerque that will double as a test.

Manager Bud Black wants to see more than health from Rusin, who missed his eighth game Wednesday with left foot plantar fasciitis.

"You hear me talk about first-pitch strikes and early-count outs -- I want to see that happening in Triple-A," Black said. "I want to see ball-strike ratios. I want to see the reports on his stuff, how's the action to his slider, the action to his cutter, the quality of his changeup, fastball command -- all the things we look for in a big league game."

Rusin, who missed time earlier this season with a right intercostal strain, is trying to return to his form from last year, when he pitched to a 2.65 ERA in 60 games. This year, he has a 6.81 in 35 contests. Rusin was used in multiple roles last year -- anything from a specialist to multiple innings. Black said realistically they likely can use him for a max of 30-35 pitches this year, as opposed to up to 50 last year.

The Rockies have put their faith in him. They didn't trade for a lefty reliever before Tuesday's non-waiver Trade Deadline, even though Black's strategy the last two games against Cardinals slugger Matt Carpenter shows a need for such a pitcher. In the current bullpen are lefties Jake McGee, who has had inconsistency similar to Rusin's, and Harrison Musgrave , a rookie who has yet to earn Black's late-game trust.

On Monday, Black stuck with righty Scott Oberg in an extended seventh-inning appearance, and Carpenter delivered a game-tying, two-run single. McGee would end up with the 5-4 loss when he yielded Marcell Ozuna 's 10th-inning homer. On Tuesday, with righty starter Jon Gray needing to be replaced with a four-run lead in the eighth, Black went to Seunghwan Oh , who coaxed a sacrifice fly out of Carpenter in the Rockies' 6-3 victory.

"It's huge to see the trust of the front office and the head coach in me," Rusin said. "I'm the same person I was last year. I know it's in there. I have to block everything else out and move ahead. It's believing in myself.

"I'm really motivated. I felt like I've been letting the team down. It's just the competitive nature in a pitcher."

LeMahieu expected back Thursday

Second baseman and regular leadoff hitter DJ LeMahieu missed his 10th game Wednesday with a left oblique stain, but participated in Wednesday's simulated game thrown by Rusin. The Rockies plan to activate him for Thursday's series finale.

LeMahieu, who has endured three trips to the 10-day disabled list this season, is batting .278 with eight home runs and 34 RBIs.

Holliday's comeback trail

Rookie-level Grand Junction announced Wednesday afternoon that onetime Rockies star Matthew Holliday , who signed a Minor League contract over the weekend, would serve as designated hitter and bat third Wednesday night against Ogden to begin his comeback. Holliday expects to play a small handful of games in Grand Junction, then join Triple-A Albuquerque in hopes of helping the big club as a bat off the bench in September.

Thomas Harding has covered the Rockies since 2000, and for MLB.com since 2002. Follow him on Twitter and like his Facebook page.