Julio Teheran’s career has been one largely defined by consistency. Over his seven full seasons in Atlanta (2013-19), he never made fewer than 30 starts or threw under 174 innings, with ERAs between 2.94 and 4.49. Arguably the most defining element of his reliability was how he consistently out-performed his peripheral numbers. In each of those seasons, Teheran considerably out-pitched both his FIP and xFIP, often by close to a full run.

On the surface, it would appear that Teheran was already declining significantly over the previous three seasons, even if his ERAs failed to reflect such a story. Like many veteran starters, the easy assumption for such a decline would be diminished stuff, but his 22.4% strikeout rate in 2018 was the best of his career to date, with his 21.5% in 2019 not far behind. Teheran’s decline in Atlanta was predominantly marked by a notable loss of control — jumping from a 5.4 BB% in 2016 to 8.9% in 2017, then 11.6% and 11.0% in 2018 and 2019, respectively. Teheran’s streak of consistent results came to a screeching halt in 2020 to the tune of an 10.05 ERA, 8.62 FIP, and 6.35 xFIP, a recipe that culminated in -0.9fWAR.

But the most worrying sign for Teheran is that this is not a continuation of the previous problem. His walk rate for 2020 was 10.7%, still worse than his career average, but a slight improvement on the previous two seasons. What’s particularly alarming is that his strikeout rate plummeted to just 13.4%, while no pitcher in baseball with more than 100 batters faced had a whiff rate lower than Teheran’s 14.6%. Teheran was only hit slightly harder than previously; while his 38.7 hard hit % was notably higher than 2018’s 36.7% and 2019’s 35.4%, his average EV allowed was only slightly worse than league average at 89.0 mph, identical to his 2019 season. When paired alongside his inability to miss bats though, this high volume of hard contact led to disastrous results. Read the rest of this entry »