Nationals right-handed reliever Ryan Mattheus allowed four earned runs in his first 15⅓ innings pitched this season.

One sudden outburst of anger took relief pitcher Ryan Mattheus out of the Nationals’ bullpen.

During a May 19 outing against San Diego, Mattheus gave up five earned runs, ballooning his ERA from 2.35 to 4.96. Unable to control his temper after he left the game, Mattheus punched his locker. He broke his throwing hand and was placed on the disabled list.

The right-hander has had time to deal with the repercussions of his momentary lapse of judgment.

“It’s probably one of the most frustrating things I’ve ever dealt with,” Mattheus said. “Being a baseball player, I’ve been on the DL. I’ve been hurt before. That kind of stuff was uncontrollable. This is something that was self-inflicted, a stupid decision. It’s been tough to swallow, tough to watch and tough that I couldn’t be out there with the guys.”

A month after the punch, Mattheus has taken the cast off and partaken in some soft tosses. He was pleasantly surprised with how the hand held up while playing catch from 60 feet away.

The main concern for Mattheus is if his arm strength will return to normal once he’s cleared to pitch in a game. As of now, it appears Mattheus is on the right track.

“The strength guys kept me on a really good program, even with my hand in the splint,” Mattheus said. “I feel I haven’t lost much. It’s going to be getting the long toss out there and the reps on the mound.”

Manager Davey Johnson said Mattheus has been dipping his hand into a bucket of rice, to help improve his grip. It’s a technique pitchers use when healthy, but something that can aid an injured hand.

“[Mattheus’ rehab is] not as much as it would be for a starting pitcher, but he has got to go through that mound work, throwing every day,” Johnson said.

Mattheus expects a minor league assignment in the near future but said on Friday that he’s probably four weeks away from returning to the Nationals.

“I hope it will be a little sooner, that’s just my own timetable,” Mattheus said. “Obviously, I want to push it more than they really can. That’s something the trainers and doctors are going to have the ultimate say in.”