The Phillies lost their No. 5 starter for the foreseeable future. They hope their All-Star catcher and slugging first baseman avoid similar fates with 15 games to play and the postseason on the line.

Catcher J.T. Realmuto and first baseman Rhys Hoskins are scheduled to have MRI exams on Monday. Realmuto experienced discomfort in his hip after running to first base in the eighth inning Saturday, the Phillies said. Hoskins feels soreness in his left forearm after a collision with Corey Dickerson at first base in the seventh inning Saturday. Philadelphia cannot afford to lose two of its best hitters. The club already is shorthanded, with outfielders Jay Bruce and Roman Quinn and infielder Scott Kingery on the 10-day injured list.

Realmuto nor Hoskins played in a pair of losses in Sunday’s seven-inning doubleheader against the Marlins at Marlins Park, which dropped the Phillies into third place in the National League East.

“It’s a real concern any time anyone gets an MRI,” Phillies manager Joe Girardi said, "but we want to get an idea of exactly what’s going on, give us a better way of treating it and know how long to expect they’re going to be out. Is it going to be three to five days? Is it going to be 10 days? What’s it going to be? So I think that’s why we’ll do the MRIs.”

Hoskins had an X-ray on Sunday, which came back negative. He said there is a chance he could play Monday, if he continues to respond well to treatment. Realmuto was unavailable to comment.

“It’s pretty sore today, but the soreness kind of let up as I got treatment throughout the day, so that’s a good sign,” Hoskins said. “Hopefully, it responds well overnight.”

The Phillies’ rotation could be in some trouble, too.

They placed right-hander Spencer Howard on the 10-day injured list with stiffness in his right shoulder. He experienced tightness for at least the past couple of days, and it continued to bother him Saturday, forcing him from the game in the fourth inning.

• Philadelphia drops twin bill, moves to 3rd in NL East

Howard will not return until Sept. 23 at the earliest. There will be four games remaining in the regular season at that point. The Phillies will be cautious. He is their top pitching prospect, and he missed two months last season in the Minor Leagues because of a shoulder issue. He will receive a MRI in Philadelphia.

“He felt actually better today, which is kind of weird,” Girardi said. “You have to find out exactly what’s there. It may have been just a stiff shoulder for whatever reason. Maybe he slept on it funny or whatever."

Howard’s injury returns right-hander Vince Velasquez to the rotation as the No. 5 starter. Velasquez moved to the bullpen following Howard’s promotion last month, but he has been the No. 6 starter as the team plays five doubleheaders in a 15-day stretch. The Phillies have two more doubleheaders after Sunday, so they will need to find other ways to eat up those innings.

Velasquez will start Monday’s series finale against the Marlins. The Phillies hoped that right-hander Zack Wheeler could pitch Monday, but they pushed back his start a second time after he nearly lost the nail on his right middle finger during a freak incident getting dressed late last week. The Phillies are concerned that if Wheeler loses the nail it will end his season.

Wheeler played catch Sunday and threw about 10 fastballs off the mound. Girardi said Wheeler felt “pretty good,” throwing at about 80 percent. Wheeler is scheduled to throw a full bullpen session Monday, which should let the know if he can pitch this week against the Mets.

Rookie right-hander Connor Brogdon replaced Howard on the 28-man roster before Game 1's 2-1 loss to the Marlins on Sunday. The Phillies optioned him after pitching 2 1/3 scoreless innings because they promoted rookie catcher Rafael Marchan before Game 2. Andrew Knapp caught both games of the doubleheader, but Marchan will play if Realmuto misses more time.

Left-hander José Álvarez moved to the 45-day IL to make room for Marchan on the 40-man. Álvarez sustained a testicular contusion on Aug. 20. Girardi said last week that he did not expect Álvarez to pitch again in the regular season, but he remained hopeful that he could pitch at some point in the postseason.