Used in a setup role to closer Steve Cishek, Morris experienced some discomfort after pitching on Saturday night at Colorado. He returned to Miami on Tuesday, and the team initially called it a right hip issue.
The reliever's status is day to day.
"He will stay in Miami and get treatment the next couple of days, and then we'll see how he feels," manager Mike Redmond said.
The Marlins wrap up a three-game series at the Angels on Wednesday. The club is off on Thursday before facing the Braves for three games at Turner Field this weekend.
Redmond didn't rule out Morris being available for the Atlanta series.
"It's just a matter of calming it down," Redmond said. "It's really on him as far as when he will be ready to pitch."
Miami acquired Morris from the Pirates on June 1 for a Competitive Balance pick in the First-Year Player Draft.
The right-hander has a 7-0 record and a 1.76 ERA in his time with the Pirates and Marlins this season. Morris has had scoreless outings in 31 of his 35 appearances since joining Miami.
"Hopefully it's not a long-term deal," Redmond said. "We're anticipating it will not be. But you never know. We'll see how he reacts to the treatments the next couple of days."
A.J. Ramos, Mike Dunn and Chris Hatcher are eighth-inning options with Morris out.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter