If Zack Wheeler’s mangled fingernail isn’t worrisome enough for the Phillies, their top young pitcher walked off the mound in the fourth inning Saturday night with shoulder stiffness.

Spencer Howard gave up a three-run home run to Miami Marlins third baseman Brian Anderson, then met on the mound with manager Joe Girardi, pitching coach Bryan Price, catcher J.T. Realmuto and athletic trainer Paul Buchheit. Without throwing any warm-up pitches, Howard left the field with Buchheit.

The Phillies have labeled the issue “right shoulder stiffness.” He exited early from an Aug. 14 start with a blister under the nail on his right middle finger but didn’t miss a start. The Phillies were holding their breath that this injury isn’t any more sinister.

Wheeler had been scheduled to start Saturday night in Miami but was scratched after ripping the nail on his right middle finger almost off the skin bed while putting on a pair of jeans Wednesday. He was scheduled to try to throw Saturday in order to determine if he will be able to pitch in Monday’s series finale at Marlins Park.

Howard breezed through the Marlins' order once, facing the minimum nine batters through three innings as the Phillies staked him to a 5-0 lead. He struck out Corey Dickerson and Starling Marte to open the fourth inning before allowing his first hit of the game, a two-out single to Jesus Aguilar.

But things devolved from there. Howard walked Matt Joyce on six pitches and gave up the homer to Anderson on a full-count slider.

There weren’t any overt warning signs that anything was wrong. Howard’s fastball velocity dipped sharply throughout an Aug. 31 start against the Washington Nationals. That didn’t appear to be the case against the Marlins. He threw at least three fastballs that were clocked at 94 mph in the fourth inning.

Howard’s first half-dozen starts in the majors have followed a similar trend. The first time through the order, hitters are 9-for-49 (.184) with five walks and 17 strikeouts against him. The second time through the order, they are 17-for-42 (.405) with five walks and five strikeouts.

With another doubleheader scheduled for Sunday, the Phillies were hoping that Howard could work deep into the game. After a first-inning grand slam by Didi Gregorius and Bryce Harper’s first homer in 83 plate appearances since Aug. 22, it seemed they would be able to ride Howard into the sixth or seventh inning.

Asked about the possibility of a long start from Howard, manager Joe Girardi said, “It would really help with knowing what we have tomorrow. It’s a big start for Spence."

The Phillies will close the season with 17 games in 15 days. With three more doubleheaders (Sunday in Miami, Sept. 18 at home against the Toronto Blue Jays and Sept. 22 in Washington), they were already going to have to use Vince Velasquez and likely a bullpen game or two even before Wheeler went down.

If Howard is out, too, the pitching depth would be tested even further.