Jose Lobaton, Stephen Strasburg and 10 knuckles. (Photo by Jonathan Newton / The Washington Post)

It started with conversations last season, when Stephen Strasburg asked Jordan Zimmermann and Dan Haren about they threw their slider and cutter. It evolved this offseason, when Strasburg fiddled with a grip and a release. It was unveiled Tuesday afternoon, when Strasburg rifled a slider – a new pitch for him – into Jose Lobaton’s mitt during a bullpen session.

In his fifth professional season and more than three years removed from Tommy John surgery, Strasburg has a reached a point at which he feels comfortable building off his current, considerable arsenal. Along with his fastball, curve and changeup, Strasburg is working to add a slider.

“It’s just a work in progress,” Strasburg said. “It’s something that I’ve been messing with. I’m just trying to get a feel for it. I’m not going to dump any of my other pitches. But I’ll just have something in the back pocket.”

Pitching coach Steve McCatty compared Strasburg’s slider to Zimmermann’s changeup, the pitch Zimmermann worked to perfect for three spring trainings before it became a meaningful, effective offering last season.

“It’s going to be something [Strasburg] can use to run the ball in on left-handers,” McCatty said. “And, in my mind, it’s a work in progress, obviously. It’s not going to be something that he uses a lot. We don’t know. We’ll see how it plays out. It looks pretty good, though.”

“You always want to tinker and make sure you get better, all that stuff,” McCatty added. “Again, we’re working on it. It could be something he uses. We’ll see how it goes. But you should always work on pitches, refining them, trying something new. Jordan got the changeup. It helped him quite a bit.”

Strasburg first considered mixing in a slider last year. He didn’t want to throw a cutter, but talking with Haren about his cutter helped him understand how to grip and finish a slider.

“I didn’t throw it last year,” Strasburg said. “I think my arm is more flexible, like I’m staying behind it more. I feel like it’s something I could use to my advantage.”

Strasburg has only thrown two bullpen sessions at spring training, so he hasn’t had much time to make progress  on the pitch in camp. But through offseason work and early returns in camp, he can tell the difference between what works and what doesn’t.

“When I try to throw it straight, it’s good,” Strasburg said. “When I try to make it move, it’s not so good. It’s kind of how it is. I think that will help my breaking ball, the mindset, sticking with that. I’ll have a better curveball, more consistent.”

Despite oddities, injuries and other assorted adversity last year, Strasburg finished last year with a 3.00 ERA and 191 strikeouts over 183 innings. And now he may have a new way to attack hitters.