The Colorado Rockies starting rotation has been awful at preventing runs this season. Their collective 6.31 ERA and 5.15 FIP are easily National League worsts, and their walk and home run rates rank at or near the bottom as well. Pitching in Coors Field plays a big part in their performance — as their much improved 4.32 SIERA and 4.44 xFIP indicate — but overall, starting pitching has been a major weakness for the disappointing 25-41 Rockies.
That doesn’t say very much for Jeremy Guthrie, who has pitched so poorly in a poor rotation that he is being moved to the bullpen. The season has been nightmarish for the usually steady 33-year old starter. His strikeout rate has dropped from around 14% to 10%. His walk rate has risen from 6.5% to 8%. His home run rate has ballooned by an entire home run per nine innings. He has managed just 59 innings over 11 starts, with an ugly 7.02 ERA, 6.72 FIP and 5.09 SIERA.
The season isn’t yet halfway over so this could all just be an extended slump bound to regress. It could also be a combination of general aging and pitching in a tougher park. However, as it currently stands, Guthrie moved to the easier league, and out of baseball’s toughest division, and has declined in literally every area. Believe it or not, this is fairly rare throughout major league history.
To more accurately model Guthrie’s situation, I searched for pitchers who had logged at least 300 innings in the junior circuit over an uninterrupted three-year period, who then pitched 100+ innings in the National League the next year. There were 197 pitchers fitting this criteria. I then calculated a weighted average of their ERA, K/PA, BB/PA and HR/PA over the three years initially spent in the American League and compared the results to their National League numbers in the fourth season.
Of the original 197 pitchers, 75 had a higher ERA in the fourth season compared to their three-year average. Of that group, 42 also struck out fewer batters per plate appearance. Only 28 of them posted worse ERAs, strikeout and walk rates. Only 17 pitchers were worse across the board (ERA, K/PA, BB/PA, HR/PA) in the fourth season.
The two most recent pitchers to fit the bill were Tim Hudson (2002-05) and Cory Lidle (2001-04). Interestingly enough, both Hudson and Lidle pitched for the Athletics in the early part of the decade before moving to the National League. Lidle spent the 2003 season with the Blue Jays, but pitched for the Athletics in 2001-02.
Hudson averaged a 3.03 ERA, 15.3% strikeout rate, 6.1% walk rate and 1.5% home run rate from 2002-04. In 2005, he posted a 3.52 ERA, 14.1% strikeout rate, 8.0% walk rate and 2.4% home run rate with the Braves.
Lidle averaged a 4.42 ERA, 14.2% strikeout rate, 6.1% walk rate and 2.7% home run rate with the As and Jays from 2001-03. In 2004, with the Reds (before being traded to the Phillies), he pitched to a 5.32 ERA with a 14.1% strikeout rate, 6.7% walk rate and 3.7% home run rate. His strikeout rate didn’t move all that much but the walks increased a bit and, like Hudson, his home run rate shot up a full percentage point.
The increase in home run rate is likely attributable to park factors and the change in venue. StatCorner calculates the home run park factor for the Oakland Coliseum at 85/82 for righties and lefties, respectively. The home run park factor for Turner Field is 95/92, more conducive to big flies. It’s easier to hit home runs in Toronto, as well, but Lidle spent the early part of the span pitching for the As, and then went to the extreme 120/113 home run park factor in Cincinnati. Again, it seems logical that his home run rate would rise as a result of the environment.
But the same can’t entirely be said of Guthrie. While Coors Field has the reputation of a hitters haven, Camden Yards has a very similar home run park factor. StatCorner has Coors Field at a 122/120 home run park factor, with Camden Yards at 125/118. In other words, it’s been easier for righty hitters to hit home runs at Camden Yards recently than at Coors Field. It isn’t as if Guthrie went from the Oakland Coliseum to a pure home run haven. It’s easier to do everything else at Coors Field, but Guthrie’s ballooned home run rate can’t merely be chalked up as park effects.
His plate discipline metrics tell an all-too familiar tale of a pitcher whose stuff simply isn’t as effective. He is falling behind hitters more frequently as they opt against chasing out of zone offerings. He then throws more pitches in the strike zone but struggles with location, and the batters get selective, swinging less frequently while making more contact. This falls right in line with his PITCHf/x data, as his primary pitches — fastball, slider, changeup — are all being thrown with less movement.
Guthrie certainly isn’t this bad of a pitcher, but as Dave Cameron discussed the other day with Tim Lincecum, it’s unfair to outright label bad pitching as bad luck. Guthrie is doing plenty wrong, and shouldn’t merely be trotted out every fifth day for the sake of doing so, even if his BABIP and other traditional ‘luck’ metrics look zany.
It’s probable that he would find his footing if given the opportunity to remain in the rotation as he has proven himself capable of pitching at an above average level. His 2.5 WAR average in baseball’s toughest division from 2007-11 is more predictive of his future success than 59 awful innings with the Rockies this season, which makes him an ideal buy-low candidate. However, it’s historically rare for someone to pitch worse in every category after switching to the easier league, which makes his situation very interesting to monitor over the rest of the season.
He isn’t this bad, but whether it’s a health issue or a severe and prolonged slump, the Rockies clearly appear to have gotten the short-end of the Guthrie for Hammel and Lindstrom deal.