Brad Lidge, Velocity and Trevor Hoffman

Brad Lidge didn’t top 90 on the radar gun Monday.

Sure, yesterday was a big first step for the 34-year-old reliever. The first appearance of the year — especially when it happens this late in a season — is an important moment for any pitcher who’s recovered from an injury. But, if the muted radar-gun readings are to believed, the outing was perhaps just one point on the long highway back to full strength — at best. At worst, he might find that his new fastball velocity will limit him to the side roads of success. That is, unless he can be legendary with his slider.

Lidge’s velocity was in line with what the Phillies saw during his eight-appearance rehab stint this summer. The 89.7 MPH that he averaged against the Padres would be two miles per hour slower than he showed last year and five miles per hour slower than his career average.

Jeff Zimmerman showed us in his excellent piece about the reliability of fastball velocities that even after one game, we can say that Lidge’s fastball is 68% likely to be within .8 MPH of its observed speed going forward, and 95% likely to be within 1.6 MPH. Since Lidge showed a two mph drop in his first game, there’s little doubt that he’ll be throwing with less gas this year.

Mike Fast famously found that pitchers gain about .25 runs allowed when dropping one mile per hour on the gun, at least until they hit 89 MPH. With a 3.87 FIP (96 FIP-) last year, even a modest prediction — say, that he gains a little velocity back and only loses one mile per hour when compared to last year — would have Lidge pitching on the wrong side of league average this year. Life in the slow lane is not as exciting.

But is it really a big deal? Point out Lidge’s reduced fastball and the names Jamie Moyer, Greg Maddux and maybe even Shaun Marcum come to mind.

And don’t forget that there’s one name that’s perhaps more germane to this discussion: Trevor Hoffman. Hoffman had plenty of success with an 85-plus mph fastball — and he did it with a top-shelf changeup. Lidge’s slider is considered his best pitch. So could it keep Lidge afloat?

Defining a pitch and its dominance is difficult. Hoffman had a changeup worth 40.2 linear weights runs since 2002. Lidge’s slider has been worth 90.9 runs over the same time period. But linear weights utility can be limited because the interactivity between pitches is so important. Hoffman got a 17.8% whiff rate on his changeup in 2009 and 2010. Lidge, in the same time period, got a 20.6% whiff rate on his slider. Hoffman’s changeup had three more inches of vertical and horizontal movement than average. Lidge’s slider moves about two inches more — horizontally — than an average slider.

We don’t hear about Lidge’s slider as much as Hoffman’s changeup, but it could be in a similar class. He’s actually used it more than his fastball in his career, so maybe he’s more suited than most to dealing with a loss in velocity. Relievers can dominate with one great pitch, and Lidge was throwing his fastball around 91 mph down the stretch last year. And he was filthy.

Now that he’s humping along around 89 mph, is it possible that he’s in for a high-speed exit from the league? Maybe. But if he sticks around, perhaps we’ll have to consider his slider among the pantheon of great pitches.