Erick Fedde has a forearm injury. (Katherine Frey/The Washington Post)

MIAMI — Erick Fedde allowed five earned runs to the Mets in his last start, and the right-hander looked far different from the pitcher who impressed the big league staff in spring training — or even the one who struggled through his first two big league outings.

One difference was his curveball, which showed dramatic improvement in that start. This qualified as a positive development for the Nationals’ top pitching prospect, who had never relied on the pitch before.

Another difference was his velocity, which was 5 mph lower than usual, sitting in the high 80s and occasionally the low 90s. Fedde’s fastball normally sits in the mid-90s. This represented a negative development for the right-hander, who was dealing with forearm trouble at the time and will not pitch again this season because of it.

Monday, the Nationals announced they had placed Fedde on the disabled list with a forearm flexor strain. That news provided both explanation and cause for concern. The flexor is the mass where tendons in the forearm connect, the place Stephen Strasburg suffered his season-ending injury last year. “Strains” generally refer to some degree of tearing in that mass. Strasburg’s injury was initially described in more vague terms, too, before he revealed he had suffered a torn pronator tendon that required so much rest he lost the final month of the season.

Fedde will miss the rest of the season with the injury, though Nationals General Manager Mike Rizzo said Fedde’s MRI exam showed no damage to his surgically repaired right elbow and indicated that the strain was far enough down the forearm so as to allay concerns that it foretells major elbow trouble.

“We shut him down out of an abundance of caution. He’s guy that would have probably missed a start or two,” Rizzo said. “But he’s been through a lot this season. We started him in spring training as a starter, tried to shorten his innings up as a reliever, and then stretched him out as a starter. So we felt this was a good time to shut him down and get him ready for next spring training.”

Fedde, who underwent Tommy John surgery in spring of 2014,  threw just more than 120 innings in the minors in 2016. This season, he has thrown 105 2/3 innings. Normally, a workload increase of 20 to 30 percent is considered safe, and the Nationals are particularly careful when it comes to innings limits.

Cause and effect always blur when it comes to arm injuries, but while Fedde’s innings count does not provide any obvious reason for concern, the nature of his workload was different than any he had experienced. When their bullpen was in shambles midway through the season, the Nationals decided to move Fedde — a career starter — to a reliever role for an impromptu crash course. That way, Fedde would have experience if the Nationals wanted him to contribute out of the bullpen in September or October, perhaps as Reynaldo Lopez did in 2016. After 16 relief appearances, the Nationals began stretching Fedde out again, moving the ultra-competitive 24-year-old back into the Syracuse rotation. Three Class AAA starts later, Fedde made his major league debut.

Though he struggled in his first two big league starts, Fedde’s stuff looked intact. He threw the slider that helped him climb the minor league ranks. His fastball bled into the high-90s now and then, but never dipped low enough to cause concern.When he returned to the minors in August, Fedde was held off a normal rotation so as to provide insurance for injured starters Max Scherzer and Strasburg. He pitched for Syracuse on Aug. 13, then again on more than a week of rest on August 21. In the last inning of that start, Fedde felt something was off, something about which Rizzo and Nationals Manager Dusty Baker knew before Fedde returned to start in the majors six days later.

“We knew what was going on in the previous start in [Class AAA], then in the big leagues,” Rizzo said. “We saw a trend, and that’s why we took the course of action we did.”

That trend, like his velocity, was headed downward. Fedde said he wasn’t worried about the five miles lost on his fastball against the Mets and figured he was just tired after a long season. When he started that day, he told his manager that he felt fine. Though he threw a career high 112 pitches that day, he never looked fine.

“I’m impressed by it because he wants to pitch, but if they’re not feeling right, you want them to say something about it,” Baker said. “… I asked him how come he didn’t say something. He said it was because he knew we had a doubleheader and we were short pitching.”

The Nationals wanted to give their starters an extra day of rest, something they planned to do this weekend, hoping Fedde would be revived enough to start in Milwaukee. Instead, they turned to Cole on Monday in Miami instead. Normally, players do not go on the disabled list in September, when rosters expand and these things do not matter. But putting Fedde on the disabled list Monday was a procedural necessity.

To activate Cole to start Monday, the Nationals needed to move someone to the disabled list, as the 10-day waiting period for a player optioned to the minors is not waived even when rosters expand in September. That 10-day waiting period is waived in case of injury. Moving Fedde to the disabled list therefore allws the Nationals to activate Cole to start Monday night. They also activated Pedro Severino, and now have four active catchers on their roster. Matt Wieters, their usual starter, will return to the starting lineup Monday after battling back pain this weekend.

WASHINGTON NATIONALS

Trea Turner SS

Howie Kendrick LF

Daniel Murphy 2B

Ryan Zimmerman 1B

Anthony Rendon 3B

Jayson Werth RF

Michael A. Taylor CF

Matt Wieters C

A.J. Cole P

MIAMI MARLINS

Dee Gordon 2B

Giancarlo Stanton RF

Christian Yelich CF

Marcell Ozuna LF

J.T. Realmuto C

Derek Dietrich 1B

Brian Anderson 3B

Miguel Rojas SS

Adam Conley P

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