CHICAGO -- Phillies right-hander Aaron Nola is scheduled to undergo an MRI on Thursday in Philadelphia after experiencing back spasms following a 45-pitch bullpen session on Monday.
Nola left the team on Wednesday for the MRI, which manager Pete Mackanin said was mostly precautionary. Nola's spot in the rotation comes up Friday, and Mackanin said Nick Pivetta would likely start against the Nationals after the Phillies return home from their seven-game road trip.
Pivetta (0-1, 3.60 ERA) gave up two runs and nine hits over five innings against the Dodgers in his Major League debut Sunday. The right-hander is ranked by MLBPipeline.com as the Phillies' No. 12 prospect.

Nola threw a simulated three innings on Monday at Wrigley Field with a break in between each 15-pitch set. According to Mackanin, Phillies pitching coach Bob McClure said Nola was a little tentative through the first two sets but that the third one was fine. Nola felt a spasm in his lower back later, which gave the Phillies reason for concern.
Mackanin said the Phillies wouldn't take any chances with the injury and that Nola will be re-evaluated after they receive the MRI results.
"He's been showing signs of getting better, but there's still a little something there that we have to make sure we get a look at it," Mackanin said.