As one of the league’s most valuable pitchers over the last several years, Jose Quintana has predomintantly relied not on generating whiffs, but inducing weak contact. As such, some of his performance metrics are somewhat at odds with one another.
His SIERA, which reads like ERA but factors in batted-ball portfolios, is currently at 4.15 and was at 3.62 and 4.01 in the last two years. But wait, doesn’t this mean that Quintana actually was generating relatively hard contact? After all, his SIERA numbers aren’t the most encouraging. In fact, you might actually see metrics like these as a reason to believe Quintana may not be as good as advertised.
Except SIERA has its own unique set of limitations, and, as the availability of public Statcast data continues to be engulfed by curious data scientists, numbers like SIERA might be relied upon less.
xStats tell a different story. While Quintana’s SIERA and xFIP were 4.01 and 4.03, respectively, last year, his scFIP (Statcast FIP) was only 3.33. This version of FIP takes into account the precise probability of a fly ball leaving the yard, rather than the league average 10.5% HR/FB rate xFIP uses. This tells us that Quintana has been very good at inducing weak contact in the form of fly balls.
Indeed, batters facing Quintana hit fly balls with an average exit velocity of 86.2 and 87.7 mph in 2015 and 2016, respectively. This year, however, his exit velocity on fly balls has been right at the league average of 89.6 mph. That’s partially why his 2017 scFIP is over 4.00. But there’s reason to believe that could come down, since fly ball launch angle takes roughly one full season to stabilize. Though we don’t have data regarding fly ball exit-velocity stabilization, I’d imagine the two are closely related, even if there is some difference in reliability.
All in all, don’t be concerned about the recent spike in fly ball exit velocity. It’s too small to tell. The Cubs just acquired a pitcher with one of the most favorable batted-ball portfolios in MLB. His xFIP and SIERA, both of which factor in some degree of batted ball information, don’t tell the whole story. The more precise data suggests that Quintana’s low-3’s ERAs are the real deal.