That opens the door for Scott Feldman, who is on the 15-day disabled list, to return against the Mariners next weekend.
Feldman, who's missed the last eight days with right biceps tendinitis, started throwing Thursday and participated in long-toss drills from the stretch Saturday.
If all goes well during his rest-filled rehab, he'd be available on May 3, 17 days after his last outing, a 5-1 loss to Kansas City.
"Our thought process when he went on the DL was to make sure he came back 100 percent, so we won't force him back into a start if he's not there yet," Porter said. "The hope is that he can be ready for then and his progress indicates he will be."
That would likely leave McHugh and Brad Peacock, who hasn't lasted longer than five innings in his two starts, jockeying for the final spot in the rotation after Lucas Harrell's recent dismissal.