Every year we hear stories about pitchers whose fastballs don’t seem to have the same life as last year. The most talked about are typically front-line starters that rely on their fastballs. In early 2013, the name that’s being discussed the most is Yankee ace CC Sabathia.

Throughout spring training, Sabathia’s velocity has been a point of concern. Coming off of elbow surgery during the offseason, Sabathia’s first regular season start did nothing to quell that concern. As The Star-Ledger’s Andy McCullough notes:

Sabathia’s fastball topped out at 91.7 mph on Monday, according to Pitch f/x data from Brooks Baseball. On Opening Day in 2012, his fastball hit 94.5 mph. On Opening Day in 2011, his fastball touched 94.7 mph.

(By the way, if you don’t read McCullough on a regular basis you are missing out.)

In the end, McCullough notes that while it’s reasonable to be concerned, Sabathia is likely to improve as the season wears on and has good enough secondary stuff to still be very good.

Overall McCullough is right, however, I think there is greater reason for concern than some may think.

Sabathia was one of the top starters I flagged as at risk for further velocity loss this season based on how far his velocity declined last year. CC lost nearly 1.5 mph off of his fastball in 2012. Pitchers that lose at least 1 mph have, on average, a 39% chance of either getting injured or failing to throw at least 40 IP in the following season. They also have a 91% chance of losing further velocity the following season.

Sabathia is a slow starter, both in terms of performance in velocity. However, in 2012 he simply started with a lesser fastball in April and never quite saw it recover to previous levels:

It’s only one start, but Sabathia’s fastball averaged around 90 mph yesterday. That would place it more than 1mph off his April velocity in 2012. As many pitchers will have slower fastballs in April compared to their overall average from the previous season, we have to compare April velocity in year one to April velocity in year 2. When pitchers are down at least 1 mph from the previous April they are four times as likely to finish the season down at least 1 mph:

So, early season velocity isn’t as much as a signal as later months in terms of a declining fastball, but it should at least raise some eyebrows.

And while Sabathia does possess great secondary stuff, the key for him to pitching with a reduced fastball will be how effective he can be in and around the zone with that pitch. As I wrote last year:

From 2009-2011, Sabathia generated -20.5 runs per 100 fastballs clocked at less than 92.5 mph. This year, Sabathia generated 21.9 runs per 100 fastballs clocked under 92.5–virtually all of his fastballs. Sabathia still put up solid numbers in 2012 (ERA- 81, 23.7% K%, 5.3% BB%), but his HR/FB rate jumped to 12.5%–highest in his career. Eighteen of his 22 home runs allowed came on fastballs (82%). The previous three years? Only 56%. All great pitchers must adjust to reduced velocity at some point, but those adjustments typically take time.

Lossing a tick off his fastball doesn’t necessarily spell doom for CC Sabathia. But given his age, usage, and what we saw last year it is quite reasonable to be more concerned about this April decline than most.