Watching Roberto Osuna pitch it’s easy to forget that he’s not a finished product.

The Toronto Blue Jays’ closer has certainly looked fully cooked this season, retiring 18 of the 22 batters he’s faced while recording four saves. Yet there’s a difference between being effective and being fully-developed.

Osuna turned 21 prior to the season, an age where most pitchers are pitching in college or the minor leagues. The Blue Jays’ top pitching prospect, Conner Greene, is only 56 days younger than the Mexican right-hander and he’s opening the season at single-A Dunedin, where he’s still two years younger than the average player in the Florida State League.

Although Osuna has already experienced remarkable success, he continues to grow and change as a pitcher. This season that progress is manifesting in the form of a new strikeout pitch.

During his rookie season, Osuna featured a potent fastball-changeup-slider mix. In 2016, his arsenal features the same pitches, but his slider has changed.

Last year, he used a hard slider that usually came in close to 90 mph, with tight, but modest break:

Now, Osuna is using a slider that is significantly slower, but has more drop:

Velocity loss on any pitch is usually cause for concern, but this appears to be a intentional move by the right-hander. He’s throwing both his fastball and changeup at the same speed as last season, only changing the slider.

This pattern calls to mind what Drew Hutchison did at the end of the 2014 season when he sacrificed velocity on his breaking ball for more movement. The modification has certainly affected the vertical movement on Osuna’s slider, where he’s gotten close to three more inches of break compared to last year.

It’s far too early to say how this change might affect Osuna long-term. Early returns are mixed. He’s gotten a couple of strikeouts on the pitch, but also gave up a line-drive home run to Travis Shaw on Sunday, popping a blister in the process.

Hutchison’s bigger breaking slider was extremely effective until it wasn’t. Baseball is a game of constant adjustments and it’s more common for them to come to nothing than lead to breakouts.

What is clear is that Osuna is tinkering. He’s not resting on his laurels and taking an “if it ain’t broke don’t fix it” approach. At his age that’s important.

Maybe he’ll eventually go back to the harder slider that served him well last year. It was undoubtedly effective, and similar to the “Dan Warthen” slider that is in vogue right now.

Star closer or not, he’s an inexperienced pitcher who’s not sure what works best for him yet. Most 21-year-olds are trying to figure out their secondary offerings. What makes Osuna so special is that he’s able to do that while holding down a closing job on a contending team.