While Hector Rondon’s Fastball Velo Was Fine in WBC, Slider Movement May be Real Issue

Despite having been hampered by a triceps injury and pitching poorly down the stretch last season, Hector Rondon hasn’t lost the faith of Joe Maddon. The former Cubs closer pitched only 9.1 innings in the second half of last year’s championship run, serving up meatballs that bloated his post-All-Star-break ERA to 6.41.

Rondon’s poor performance in the World Baseball Classic doesn’t alleviate fans’ skepticism, but Maddon was impressed with the his setup man’s velocity while pitching for Venezuela. Even if the radar gun says good things about the fastball, though, PitchFX data from the WBC suggests Rondon’s slider isn’t ready.

Struggling to throw sliders spells doom for Rondon, who throws the pitch close to 35 percent of the time. At his best, Rondon induces one whiff for every five sliders, a rate higher than 74 percent of all other MLB sliders. At his worst, such as August and September of last year, Rondon’s key offering was roughly one inch flatter than the typical 3.4 inch movement he averaged.

In short, a broken slider means a broken Rondon.

Those are his numbers with the Cubs, but how did his slider look in the World Baseball Classic? Not good. You may need to tilt your head and strain your eyes to see that lonely red dot on the below chart. Maddon might’ve loved the Venezuelan’s velocity — indeed, he was bringing the heat at 96.4 MPH — but he certainly didn’t love seeing those cement-trucks spinning toward the plate.

Of course, Rondon only threw 17 pitches in the tournament, a mere four of which were sliders. Extrapolating such a small sample into a prognosis of imminent doom would be silly, but monitoring slider movement might be worthwhile as we see more of them throughout the season.

Personally, I think Rondon will be fine because he did bounce back to regain some of his movement late last season. As long as the righty is healthy and continues to progress toward his form of old, I have all the confidence that he and Wade Davis will be successful in high-leverage moments.