Explaining Mariano’s velocity dip in 2009

Yesterday, after throwing his first bullpen session of the spring, Mariano Rivera, a timeless fixture in the Yankees bullpen, discussed a topic which he rarely needs to address—his own fragility. The 40-year old Rivera underwent surgery prior to the 2009 season in order to remove a bothersome calcification from his right shoulder. When asked about the shoulder last spring, Rivera would flash a smile to reporters and and say that he was alright. However, after firing 21 fastballs yesterday, Rivera and his manager, Joe Girardi, finally admitted that, as a result of the calcification procedure, the greatest closer of all time did struggle to develop his arm strength well into the regular season.

“It was hard, but it wasn’t impossible,” Rivera noted when asked about the surgery’s strength-sucking affect on him last year. “I took the challenge and it worked,” he said, adding that his rehab was done during the regular season as opposed to Spring Training. Girardi furthered Rivera’s story, saying that it took “a good six weeks to two months” before Rivera’s arm strength had fully returned. “I know he’s a lot further along than he was at this time last year,” Girardi stated. “At times he couldn’t extend [his arm] early on in camp. He had none of those issues [Monday].”

This news, of course, should please Yankee fans, mainly because it helps to lessen the concern some might have regarding the velocity issues Rivera experienced a year ago. In 2009, after Rivera’s four-seam fastball and cutter had averaged 93.1 mph and 92.8 mph in 2008, the average velocity of his four-seamer dipped to 91.8 mph and the average velocity of his cutter fell to 91.3 mph (the lowest velocities on record for Rivera). When one considers Rivera’s age, the loss in velocity is significant, and could indicate a continued loss of velocity going forward. A lack of arm strength certainly gives a reason for the velocity decrease though (in part, age could still be a relevant factor), and when you look at a month-to-month view of his average velocity, Rivera’s fastball saw an uptick in speed in September and October (the cutter did not). Even if the lack of velocity is real, Rivera locates well and generates great movement to get outs. Still, we can be optimistic about his pitch velocity going forward as he is a full year removed from shoulder surgery and he will likely have better arm strength for the entire season, whereas that was not the case for 2009.

Photo by the AP