Erick Fedde allowed a run in two innings in his spring debut Monday. (Jonathan Newton/The Washington Post)

LAKE BUENA VISTA, Fla. — Erick Fedde knew something was wrong. His right forearm was hurting before his start against the New York Mets last August, but the pain intensified during the outing, producing a precipitous drop in velocity.

Fedde wasn’t too alarmed, and evidently the Washington Nationals’ coaching staff wasn’t either, allowing him to log six innings despite knowing of the soreness beforehand. Fedde figured the pain in his forearm was somewhat normal at the end of a long regular season. Then he was informed doctors also would examine his elbow.

“That was when I had a little bit of a panic attack,” Fedde recalled.

An MRI exam revealed a healthy elbow. It actually looked fantastic, Fedde was told, the kind of news that soothes nerves for a pitcher three years removed from Tommy John surgery. Nonetheless, Fedde was shut down because of a forearm flexor strain, a disappointing conclusion for one of the top pitching prospects in baseball, but he was healthy by the end of the regular season. After a typical winter’s work, he reported to spring training this month healthy and eyeing the final spot in the Nationals’ starting rotation.

“We do want to make sure that we’re careful,” Nationals Manager Dave Martinez said. “The most important thing in spring training for me is everybody leaves here healthy. Just want him to go out there and get his work done.”

On Monday, Fedde, a day after his 25th birthday, stepped on a mound for his first live action since that start last August to begin his case for the vacancy. He allowed one run on four hits and a walk in two innings against an Atlanta Braves lineup that resembled the one projected for Opening Day. Two of the hits, including a two-out hit that led to the run scored, were groundballs through an infield shift. The lean right-hander tallied one strikeout, one walk and 38 pitches — 23 for strikes. The Nationals lost the game, 2-1.

If radar guns at Disney-themed spring training sites are to be trusted, Fedde’s fastball ranged from 93 to 96 mph, which would be an encouraging return to the velocity that made him the Nationals’ top pitching prospect last year after Lucas Giolito and Reynaldo Lopez were traded as part of the deal that brought Adam Eaton to Washington.

“I’ll take it as a pretty mediocre outing,” Fedde said. “I felt really good. I felt like my stuff was ahead of even where I wanted to be. Just I think I got a little anxious and hurried. Maybe put myself in a bad spot in the second inning. Overall, pretty happy.”

A.J. Cole and Edwin Jackson are Fedde’s main competition for the fifth starter spot. And that’s if the Nationals don’t sign one of the three established big league free agent starters still available: Jake Arrieta, Lance Lynn and Alex Cobb. Club officials have said Cole is the internal favorite because he impressed them down the stretch last season. Cole also doesn’t have a minor league option remaining, which means the Nationals could lose him to another team if he doesn’t make the Opening Day roster.

But Fedde has the higher upside, the kind of potential that prompted the Nationals to convert him to reliever midseason last year in hopes he could reach the majors more quickly. Fedde made his first relief appearance May 16. By July, the experiment was aborted after 16 relief appearances for Class AA Harrisburg and Class AAA Syracuse. He made his major league debut at the end of the month, as a starter, against the Colorado Rockies.

“I tried to take it really openly,” Fedde said. “I understood the team was trying to get me to the big leagues. So how can I be upset about that? But, yeah, it was different. I had never been in the bullpen.”

Fedde wound up starting three games in the majors, posting a 9.39 ERA, 15 strikeouts and eight walks in 15 1/3 innings before he was shut down. He said he learned a few lessons, namely mistakes are punished at a higher rate and attacking batters’ weaknesses is paramount.

“I learned more in those three starts than I learned in my whole life,” Fedde said.

He was encouraged by the progress his change-up made last season but thought his slider, historically his best secondary offering, regressed. A priority this spring is to recapture that pitch, and he said he has talked to Stephen Strasburg about it. He was pleased with his slider Monday. He threw it for strikes early in the count and generated a few outs with it. Most importantly, he emerged completely healthy. There was nothing to panic about. He is himself again.