(Henny Ray Abrams/AP)

Stammen, a long reliever, has been one of the Nationals’ most valuable, versatile and, recently, dominant pitchers. In his last three appearances, he has struck out nine while allowing four base runners in four innings. Thursday, he struck out the side on 10 pitches. So, what’s gotten into Stammen?

“I haven’t changed a whole lot,” he said. “I’ve just gotten a little bit better at everything I do. Part of it is being healthy for a couple years now. The other part of it is being in the bullpen rather than starting, letting it all hang out there.”

In the bullpen, Stammen said, he doesn’t need to try to navigate the opening innings with his fastball only, as he did when he started in 2009 and 2010 in the majors and last year in the minors. He can throw more sliders, his best pitch, the one he gets hitters to swing at and miss most.

Stammen has struck out nine of the last 16 batters he’s faced, eight of them swinging. Hitters have missed 37 percent of the pitches they’ve swung at from Stammen. On his recent tear, Stammen has produced 13 misses in 59 total pitches.

“It tells me that everything is playing off my sinker,” Stammen said. “It makes me realize that stuff is all coming out of the same arm slot. It’s got a lot of depth to it to where they can’t really recognize what it is.”

Manager Davey Johnson does not envision giving Stammen a more prominent role in the Nationals’ bullpen. He has pitched late in games, in important spots, because the Nationals have played so many extra-inning games. If they stop playing them, the Nationals’ rotation could make long relievers almost obsolete.

“What I don’t like to do is start auditioning for different roles,” Johnson said. “I like to make a decision on how I’m going to use them and pretty much stay that way. He’s invaluable as a [right-handed long reliever]. It doesn’t mean I wouldn’t use him later in the game.

“But once you start changing the roles around and getting him mentally prepared for doing that, then I don’t have a right-handed long. It’s all about mental preparation. You can vary a guy’s role, occasionally, out of the need. But he’s a workhorse.”

When asked if the Nationals’ staff would have room for Stammen once Chien-Ming Wang returns and Ross Detwiler returns to the bullpen, Johnson drew a long breath and exhaled slowly. “Probably not,” he said. “That’s a question for [GM Mike] Rizzo. I know I’m not going to 13 pitchers.”

Between now and then, the Nationals could very well have a post open up due to an injury; such is the nature of pitching. If not, Stammen could return to starting at Class AAA Syracuse.

“I’m having some success as a reliever, so I’ll see how that plays out,” Stammen said. “I always view myself as a starter, but we’ll see how it all plays out. There’s a plan out there for me somewhere.”