The move will become official before the game when the club places Ty Wigginton, who has not played since suffering a strained left oblique last Tuesday, on the 15-day disabled list.
Rockies manager Jim Tracy decided not to start the left-handed hitting Stewart against D-backs lefty Joe Saunders, but Stewart figures to be in the lineup against righties Barry Enright on Wednesday and Ian Kennedy -- Stewart's teammate at LaQuinta High School in Garden Grove, Calif. -- on Thursday.
Injuries throughout Spring Training robbed Stewart of preparation time, and the result was a 2-for-26, 11-strikeout start to the season before the Rockies optioned him to Colorado Springs. Stewart hit a grand slam in his first Triple-A at-bat, and he went 13-for-36 (.361) with three home runs and 13 RBIs overall.
"I feel good," Stewart said. "I feel like I got the at-bats I needed, the playing time that I needed and the back-to-back starts I needed to get my swing right."
If his swing is right, Stewart could give the Rockies the production they've lacked from third base. Jose Lopez has struggled to a .149 batting average with two home runs and eight RBIs.
Wigginton also has struggled. A 3-for-4 performance, with his second home run and 10th RBI of the season, on the night he was hurt lifted his batting average to .233.
Stewart hit .228 with 25 home runs and 70 RBIs in 2009, his first full season. He improved the average to .256 last season, but his totals fell to 18 homers and 61 RBIs. Missing a key month late in the season with a strained right oblique, however, contributed to the drop in his power numbers.
Thomas Harding is a reporter for MLB.com. Read his blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.