Renteria was subbed at half-time of the Crew's CONCACAF Champions League 1-0 win over Santos Laguna on Wednesday with a groin injury whilst Marshall copped a kick in the head and is under a cloud.
"He didn't pull anything," Warzycha said of Renteria. "He just said something was not right."
As for Marshall: "Knowing Chad, probably he'll be fine, He needs some rest anyway. If he's not ready to play, he's not ready to play."