Julio Teheran, and Where Expectations Diverge from Reality

When evaluating pitcher performance, xFIP is a logical place to start. It controls for the various defenses that play behind any given pitcher, ballpark effects, and the sequencing of plays. There is good evidence that a metric like xFIP better captures a pitcher’s performance than ERA does. 

Of course, xFIP and ERA still cannot tell a complete story of performance, nor do they regularly match up exactly for pitchers. Because sabermetric-centric baseball fans and pundits generally defer to the family of FIP metrics, FIP is usually the stake to which a pitcher’s predicted future performance is tied to. 

Should a pitcher’s ERA sit north of his FIP/xFIP, that particular pitcher is said to likely soon experience brighter days. Should, on the other hand, a pitcher’s ERA sit below his xFIP, he is considered to be outperforming his true level of performance and soon be due for regression, and this time not the good kind.

But that isn’t always the case. Some pitchers, despite representing considerable sample sizes, seem to post ERAs that remain stubbornly distant from their FIP values. This post focuses in on one such individual: Julio Teheran. Teheran’s career xFIP is 0.73 higher than his career ERA, the widest margin among active starters with >750 IP.

Teheran, a native of Colombia, has been a noteworthy name to baseball fans for awhile now. After making his debut in 2011, at the ripe age of 20, Teheran played his first full season in MLB in 2013. In that year, his age 22 season, he placed fifth for the NL Rookie of the Year award on the back of an impressive 185 IP, 3.20 ERA (3.76 xFIP), 2.5 WAR campaign. 

Fast forward a half decade, and Teheran is right where he started: making quality contributions to the Braves’ rotation while outperforming his peripherals on an annual basis. His sample hasn’t been modest either: this January Teheran had 6 full years of service time under his belt and at the time of this writing has pitched more than 1,300 MLB innings. 

The figure below charts all active pitchers who have made more than 750 IP in starts based on career ERA and xFIP.  As aforementioned, over the course of his career, Teheran has consistently prevented earned runs more effectively than the Sabermetricians traditional yardstick might have estimated.

During the season with the widest margin, Teheran’s ERA was nearly a full run (0.92) lower than his xFIP. In 2015, the season with the slimmest margin, Teheran’s ERA was still lower than his xFIP (by 0.14). Here is a quick table to summarize some of the illustrated data above.

So why exactly is this? Why has Julio Teheran outperformed a strong indicator of future performance each year of his nearly 7 year career?

First, it appears as though Teheran has effectively maintained this trait despite a near Kershaw-ian decline in velocity. In his first full season in 2013, Teheran’s average fastball veto sat comfortably north of 93 mph. To this point in 2019, it’s hovering on either side of the 90 mph threshold. Despite this drop off, Teheran continues to employ a fairly consistent distribution of pitch usage (here in striking contrast to Kershaw). 

As a second point of consideration, here is a glimpse of some of the FIP building blocks for the 750+ IP starter dataset at large versus Teheran’s own stats.

As you can see, Teheran’s performance, on average, definitely lends to some bearish FIP manifestations. He walks more batters, strikes out fewer, and allows more home runs than the average (and median) tenured, active starter. Home runs, in particular, are troubling. Allowing 0.14 more home runs per 9 than the median pitcher in this cohort, extrapolated over 1,300 innings, results in over 20 more home runs allowed over 6.5 seasons (maybe 3 more preseason on average).  

So that more explicitly illustrates why FIP doesn’t love Teheran. But why does he so consistently outperform it? Here are a few more statistics that capture the type of contact that Teheran allows against his fellow starters.

This table tells a bit of a story. First, Teheran is a fairly extreme flyable pitcher as evidenced by his comparatively slim roundball rate. Despite this fact, that high launch angle contact is partially neutralized by a lower HR/FB ratio (something pitchers are said to “kind of” be able to control). 

What’s more, Teheran has done a great job both keeping runners off the bases and leaving them there when they do get on. His LOB% is huge in relation to the average and BABIP% relatively minute. His flyable tendency is also a logical driver for the low BABIP. A low BABIP in turn  suggests fewer baserunners and less damage when hitters do go yard against him at an above average frequency. Really, the first table illustrated why FIP hates Teheran; this second table explains why he gives the predictive aspect of FIP fits.

This sizable gap between his actual performance and suggested performance might be part of why Teheran has remained with the Braves. His poor peripherals and declining velocity would likely scare away many suitors, but his consistent quality has kept him pitching every fifth day with the Braves for over a half decade.

The Braves have a team option on Teheran for 2020, otherwise he is set to be a first-time free agent. Projecting his salary should he become a free agent could be a prickly chore given all these points. This year especially Teheran is leading a double life between his expectations and reality, with a ERA-FIP difference of an astounding -1.07. In the meantime, it’s a pleasure watching Julio Teheran continue to silence the doubters.