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.”