Jordan Hicks has been a polarizing arm for the St. Louis Cardinals. He owns the highest fastball velocity in MLB. It has a peculiarly low spin rate at an average of 2116 rpm. It doesn’t induce many whiffs, but it induces a lot of ground balls. It has difficulty finding the strike zone.
When the Cardinals take on the Miami Marlins, we are likely to see a similarly spectacular arm across the diamond. Tayron Guerrero owns the fourth highest fastball velocity in MLB. It, too, exhibits a rather low spin rate, averaging 2102 rpm. It induces more whiffs but fewer ground balls than Hicks’. It doesn’t find the strike zone frequently, either.
To call these two fastballs similar is an oversimplification, but I don’t want to get caught up in the weeds. Both fastballs are thrown very hard and they don’t spin much. It is a weird combination. They are big-time outliers.
Averaging 98+ mph on your fastball is rare. When you throw with that kind of velocity, spin rates around 2100 RPM are also rare. Jose Alvarado does it too, and he also plays for a team in Florida. The Cardinals aren’t about to play the Rays, though, so we’ll stick to talking about Guerrero for now.
The biggest knocks against Hicks have centered on his low strikeout rate and high walk rate. Guerrero hasn’t had the same strikeout issues, but he’s experienced similar problems with his control. While Hicks has benefited from an incredibly low batting average on balls in play (BABIP) and exactly zero home runs allowed, Guerrero has suffered the opposite luck. In 26 innings, he owns a 5.88 ERA. He’s a walking, flame-throwing example of how throwing hard exclusively isn't good enough.
Guerrero’s fastball might be the main attraction these days, so let’s take a quick look at a couple thrown during a strong outing on April 30. Why so far back? Because it was a good outing and I like the camera angle.
Even though Guerrero’s fastball is classified by Brooks Baseball as a four-seamer, it can still generate some heavy sink. Originally, the pitch algorithm classified this one as a two-seamer or sinker. It was nasty.
When Guerrero’s fastball gets up in the zone, it plays more like a true four-seamer. This one rides up and in, generating a whiff just above the top of the strike zone.
Beyond the fastball, Guerrero also mixes in a mid-80’s slider about 20 percent of the time. That should sound familiar. Against Guerrero’s slider, hitters are managing a meager .254 wOBA this year and a .175 xwOBA. This slider induces a whiff nearly 30 percent of the time. Here it is getting Giancarlo Stanton to swing over the top:
Then again for strike three:
Back at the end of April, Fish Stripes of SB Nation labeled Guerrero a “relief ace.” At the time, he had a 40 percent strikeout rate and a 2.71 FIP (his ERA sat at 5.11, but we know what to do with a month’s worth of reliever ERA). Guerrero had the makings of a big-time reliever.
Since that article, Guerrero’s already-bad ERA has risen to 6.59 and his FIP to 5.01. It’s impossible to pinpoint the exact reason for Guerrero’s regression. We can, however, point towards probable factors. One of those probable factors is Guerrero’s slider. The fastball made the headlines, but the slider might have been the key. And yet, he began using it less frequently.
As Guerrero’s use of the slider has fallen, so too have his chase and swinging strike rates. Those concepts are related. While Guerrero doesn't generate an exceptional chase rate with his slider, he kept hitters mostly honest by mixing it in regularly. Lately, he's become even more predictable. Fastballs are relatively easy to hit if you know they’re coming, even when they’re coming 98 mph.
Tayron Guerrero possesses an electric arm. He is probably the second-most electric arm the Cardinals have seen this season. Unfortunately for Guerrero and the Marlins, electric and good are two very different things. Thus far for Guerrero, the obvious electricity simply hasn’t translated to results.