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Thoughts on Chicago Cubs rookie Randy Rosario

Bullpen lefty having solid rookie season

MLB: San Francisco Giants at Chicago Cubs Dennis Wierzbicki-USA TODAY Sports

From the Minor League Ball mailbag:

“I don’t remember hearing much about Randy Rosario but he’s having a good season so far. Tell me about him. How would you grade him?”—-Claude the Cubs fan from Chicago

Sure thing.

Randy Rosario was originally signed by the Minnesota Twins from the Dominican Republic in 2010. He moved up gradually through the system, missing most of 2014 with Tommy John surgery and never quite breaking through as a starter, but turning a corner with his performance after converting to the bullpen in 2017.

The Cubs picked him up on waivers last November and, indeed, he’s been useful out of the bullpen so far this year, posting a 1.89 ERA in 19 innings with an 11/9 K/BB.

He reached the majors briefly with the Twins last June and at that time we wrote this profile. The key points:

Listed at 6-1, 200, Rosario is a left-handed hitter and thrower born May 18, 1994. As a starter his typical fastball was right at 90 MPH but in the bullpen the heat has kicked up to 94-95 with peaks at 97. His slider is inconsistent but is a plus pitch at its best, and his command of both offerings has improved in the bullpen. He was holding left-handed hitters to a mere .160 average with Chattanooga, and right-handers weren’t much better off a .172.

Rosario has found his niche in the bullpen and could have a long career as a middle man.

Digging deeper on the stuff, Brooks Baseball has this:

His fourseam fastball has heavy sinking action, generates a very high amount of groundballs compared to other pitchers’ fourseamers, generates fewer whiffs/swing compared to other pitchers’ fourseamers, has well above average velo and has slightly less natural movement than typical. His slider is much harder than usual and has some two-plane movement. His sinker generates an extremely high number of swings & misses compared to other pitchers’ sinkers, is an extreme flyball pitch compared to other pitchers’ sinkers, has well above average velo and has some natural sinking action. His change is thrown extremely hard, generates an extremely high number of swings & misses compared to other pitchers’ changeups and results in more flyballs compared to other pitchers’ changeups.

As you can see, Rosario has the multi-pitch repertoire (two different fastballs, slider, change) normally associated with a starter. I suppose he might return to that role eventually but for now the bullpen suits him well, with the increased fastball velocity in shorter outings making all of his pitches more effective.

Going forward, I’d like to see a higher strikeout rate. Overall I had him as a Grade C+ prospect previously and will stick with that.