Morales is 0-3 with a 4.09 ERA with two blown saves in five chances while filling in for closer Huston Street, who started the season on the DL with inflammation in his right shoulder.
Street threw a bullpen session Tuesday at Coors Field before the Phillies-Rockies game was rained out.
The Rockies had planned to replace Morales with right-hander Edgmer Escalona, but with the rainout, Escalona was sent back to Triple-A Colorado Springs. Instead, Jason Hammel, who will start the second game in Wednesday's doubleheader, will replace Morales on the 25-man roster.
Morales "is pain-free," manager Jim Tracy said. "So as a result, there are no tests that they feel need to be done at this time." He said the only prescription is exercises to strengthen his shoulder.
Street said he wasn't scheduled for another bullpen session Tuesday but talked the trainer into letting him throw 13 pitches.
Street said he was careful not to overdo it, especially with Morales on the shelf.
"The team needs me back healthy," Street said. "As greedy as I want to get, it serves no purpose for me to come up here and give up crooked numbers."
The plan is for Street to pitch three times for Colorado Springs after his time at Double-A Tulsa and for him to be re-evaluated May 24.
"Hopefully I'm pitching strong enough to merit activation," Street said.
Street, who signed a three-year, $22.5 million contact over the winter after converting 35 of 37 saves last season, missed all of spring training and has been slowly working his way back.
For now, the Rockies will go with Manny Corpas as their closer even though his meltdown in the ninth cost Colorado in a 9-5 loss to Philadelphia on Monday night.
Tracy said Corpas was so amped up that he overthrew his pitches, including an 0-2 fastball that hit Ryan Howard, who took second on a wild pitch and scored the tiebreaking run on Carlos Ruiz's single before pinch-hitter Ross Gload sent a 3-1 pitch from Corpas over the wall.
"He overthrew everything last night," Tracy said. "All you have to do is go back and check out his velocity readings where he was trying to get it up to 93, 94. And I watched him the other day in San Diego sit at about 89 or 90, make his pitches with deep sink, throw his strikes to both sides of the plate and get one hitter out after another.
"He overthrew, that's all. And he wanted to make a statement. And he tried too hard to do so," he said.