Pitchers Who Leave Colorado

Juan Nicasio has been the fantasy headline of spring among pitchers, and despite a rough outing on Tuesday that inflated both his ERA and walks per nine to 5.00 through a pair of starts, his 11.0 strikeouts per nine will keep us interested for at least a month or two. Many have speculated that Pirates’ pitching coach Ray Searage may have fixed Nicasio, and Paul Sporer yesterday shared evidence of Searage’s mythical powers. It will take some time to learn whether Nicasio’s control has really improved, but his ERA and strikeout rate with the Dodgers last year suggest that getting out of Coors Field had at least a hand in the healing process.

Weirdly, it’s not even Nicasio that inspired me to write this column. It’s Jhoulys Chacin. Chacin was thoroughly off my fantasy radar well before he left Colorado. I had to turn to our stats pages to remember that he made four starts for the Diamondbacks in 2015 after spending the bulk of the year in Triple-A and dealing with shoulder injuries. But on Tuesday, Chacin made a start for the Braves against the Nationals in which he struck out eight batters, walked none, and did not allow a run. More than likely, that start means nothing. For one, it was a spot start. He could be back in the minors if the team calls on one of their starter prospects like Mike Foltynewicz or Aaron Blair. For another, it was one game, and bad pitchers have good games all the time. But Chacin’s success coupled with the excitement about Nicasio got me thinking about pitchers who leave Colorado.

We know that Coors Field dramatically favors hitters over pitchers. Our 2015 Park Factors show that Coors allows 17 percent more runs and 13 percent more home runs than an average park. It’s easy enough to make those adjustments to pitcher projections for the pitchers who move from Colorado to a new team, but Chacin and Nicasio made me wonder whether Coors Field might have greater ramifications on pitchers who routinely have to throw there. Could it affect their pitch selection? Their aggressiveness? Is it possible that a pitcher who leaves Colorado could improve more than the park factors would suggest because of psychological benefits?

To test this, I looked at pitchers who played in Colorado since 2002 and later switched teams. I chose a cutoff of 20 innings pitched for the Rockies in the two seasons before changing teams as well as 20 innings pitched in the two seasons after leaving the Rockies. There were 79 such pitchers, most notably including Mike Hampton, Ubaldo Jimenez, and Huston Street.

In order to create comparable lines in Colorado and elsewhere, I took weighted averages of innings, strikeouts, walks, home runs, and earned runs before and after the move. That’s best explained in an example. Take a pitcher who struck out 40 batters in 50 innings in Colorado and then struck out 450 batters in 500 innings elsewhere. It’s not fair to count all of his accumulated strikeouts at both stops because he threw more innings away from Colorado, so his abilities would influence the line away from Colorado more than it would in Colorado. The weighted average simply pro-rates both lines based on the minimum of the two totals of innings. So in this example, I would count 40 strikeouts in 50 innings in Colorado and count 45 strikeouts in 50 innings away from Colorado.

Meanwhile, because I wanted to test whether the changes in pitcher stats were a result of more than just park factors, I created those weighted average lines for pitchers in all of their starts before and after, only home starts before and after, and only road starts before and after. My hypothesis was that pitchers would definitely see improvements in only home starts after leaving Colorado, but they would only improve in road starts if there was psychological benefit to leaving a situation that constantly put you in such an unfavorable park.

Here are the cumulative pitcher stats while in Colorado:

Pitchers’ Last 2 Seasons in Colorado
Split FI K/9 BB/9 HR/9 ERA
All 6593.1 6.47 3.83 1.07 4.98
Home 3316.2 6.48 3.63 1.20 5.42
Road 3345.1 6.50 4.06 0.98 4.67

Here are the cumulative pitcher stats away from Colorado:

Pitchers’ First 2 Seasons after Colorado
Split FI K/9 BB/9 HR/9 ERA
All 6593.1 6.60 3.62 1.06 4.44
Home 3316.2 6.45 3.44 1.01 4.32
Road 3345.1 6.77 3.83 1.12 4.56

And finally, here is the difference between the two:

Difference
Split K/9 BB/9 HR/9 ERA
All 0.13 -0.21 -0.01 -0.54
Home -0.03 -0.19 -0.19 -1.10
Road 0.27 -0.23 0.14 -0.11

As expected, pitchers saw pretty major improvements in their home starts after leaving Colorado. Most notably, they allowed 0.19 fewer home runs per nine and cut 110 points off their ERAs. However, results are much less dramatic in road starts before and after the move. Strikeouts and walks per nine do improve by 0.27 and 0.23, respectively, but pitchers allowed 0.14 more home runs per nine in road starts after leaving Colorado. Perhaps one benefit of playing your home games in Coors is that it takes the most extreme hitters park out of your road park rotation. All told, pitchers saw only an 11 point decline in their ERAs in road starts after leaving the Rockies, so if there is a psychological boost to not having to deal with Coors all the time, it does not have much of an impact.

Still, the park factor difference should not be ignored. In total, pitchers who left Colorado saw a 54-point drop in ERA, and both Nicasio in Pittsburgh and Chacin in Atlanta are currently in home parks that are more pitcher-friendly than average. For Nicasio, that means you definitely shouldn’t drop him after the one bad start. His strikeout rate makes him a potential top 40 starter if he can really improve his control. For Chacin, I want to see more. His career 6.9 strikeouts per nine are uninspiring, and he is not showing a change in velocity or pitch mix that would suggest a change in his skill set.

We hoped you liked reading Pitchers Who Leave Colorado by Scott Spratt!

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Scott Spratt is a fantasy sports writer for FanGraphs and Pro Football Focus. He is a Sloan Sports Conference Research Paper Competition and FSWA award winner. Feel free to ask him questions on Twitter – @Scott_Spratt

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Mr. Jason Hammel has shown flashes of rosterability since serving his 3 year Mile High sentence.