An aging Mariano?

Here are two interesting numbers for you:

91.9 and 91.4

91.9 mph is the average velocity of Mariano Rivera’s fastball and 91.4 mph is the average velocity of Mariano’s cutter. These numbers are for this season and are noteworthy as they both signal a significant downturn in Rivera’s overall pitch velocity. In the past, Mo’s fastball has been in the 93 mph range (his career velocity is 93.3 mph) while his cutter has been in the 92-93 range (the pitch has a career velocity of 92.7 mph). Even in 2008, Mo’s fastball typically sizzled at 93.1 mph and his cutter was equally imposing at 92.8 mph (on average). The velocity was there just a year ago, however, a year later we’ve seen a noticeable loss of power on his two primary (and only) pitches.

Mariano and co. seem to have noticed this, too, as Mo is throwing fewer fastballs than ever before. Instead, he’s choosing to throw his cutter more frequently as it is a pitch with enough movement to shoulder the loss in velocity. This season, Mo has only thrown straight fastballs 8.2% of the time, while he has thrown the cutter 91.8% of the time. In the past, fastball usage was a lot higher for Rivera as the percentages between it and his cutter were fairly close. That changed in 2007, though, with Rivera using the cutter more often by a significant margin (73.2% versus 26.7%). Since ‘07, he has relied mainly on the cutter and in ‘08, when his velocity dropped a bit, Mo used the cutter even more than he had in 2007. Now that his velocity has dipped even further—which may be the result of a combination of things, including age, shoulder soreness and offseason surgery—the fastball has essentially fallen to the wayside and Mo seems to be fine with that as long as his cutter is working.

To further support this theory, one can also look at pitch type values at Fangraphs for more data. You can read about the data here, but as David Appelman notes, the main crux of the data is to “see in runs the actual effectiveness of each pitch.” In 2009, Mariano Rivera’s fastball is valued at -1.4, meaning that, when compared to the league-average fastball, Mo’s fastball is 1.4 runs below average. This is the lowest rating for his fastball on record and is his only negative value, an issue that seems to coincide with the loss in velocity. For comparison purposes, Mo’s cutter is 15.5 runs above average, which is obviously why he uses it as often as he does (the movement and, of course, command allow it to be as effective as it has been). These numbers may seem randomly generated to some, but the wFB value appears to be in agreement with what we’ve seen this season in relation to Rivera’s “fading” fastball.

It will be interesting to see how Rivera’s fastball and cutter look in 2010. It may jump back up to the 93 mph range with a full winter to rest up, however, it may also continue to decrease as he ages. He has still been very effective—one of the best pitchers in baseball—yet his 1.04 HR/9 rate may be foretelling (it’s the highest HR/9 he has had since 1995). If his velocity falls even more next season, it’ll be interesting to see how he performs and whether or not he is brought back for 2011 and beyond.