"He still feels tightness," Mackanin said. "I don't want to go five or six or seven days to wait and see if he'll be OK. I'd rather have something to show for it."
In 29 games this season, Nava has been one of the Phillies better hitters. In 59 at-bats, Nava has a .305/.425/.458 slash line.
With Morgan as Nava's replacement, the Phillies currently have just three outfielders on their active roster: Odubel Herrera, Aaron Altherr and Michael Saunders. However, utility men Brock Stassi and Ty Kelly could play the outfield if called upon.
Morgan is back for his second stint in the Majors this season. In two relief appearances, Morgan has allowed seven earned runs in six innings.
Stephen Pianovich is a contributor to MLB.com based in Philadelphia. This story was not subject to the approval of Major League Baseball or its clubs.