With the Rockies having off-days Monday and Thursday, they were able to move De La Rosa to Friday's game at home against the Padres with little disruption to the rotation.
Dugger said De La Rosa experienced discomfort before his latest outing, when he held the Rangers to two runs and three hits in six innings of a 9-2 road victory on Tuesday night. He felt the spasms while running sprints the following day.
"He probably could make the start if we wanted him to, but it's better that we have him throw a bullpen Tuesday, back him up a couple of days," Dugger said.
After starting 0-3, De La Rosa has won his past four decisions while posting a 2.63 ERA with 16 strikeouts against 11 walks and a .230 opponents' batting average.
The starters in Kansas City will be Morales on Tuesday and righty Jhoulys Chacin (0-1, 4.91 ERA) on Wednesday. Both will be working on four days' rest.
Thomas Harding is a reporter for MLB.com. Follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.