Red Sox starter Rick Porcello a disaster waiting to happen in Coors Field

Boston Red Sox starter Rick Porcello’s struggles this season make him a poor fit for pitching in Coors Field where he’ll face the Rockies.

Rick Porcello‘s miserable season is about to get worse as the Boston Red Sox travel to Coors Field to face the Colorado Rockies.

This has been a season to forget for the veteran right-hander, who enters the day with the most earned runs allowed while ranking next to last in the league among qualified starters with a 5.49 ERA.

The thin air in Colorado won’t do Porcello any favors, as the ball tends to fly out MLB’s most hitter-friendly park. ESPN’s MLB Park Factors ranks Coors Field as the top ballpark in the majors for scoring runs and third-highest for home runs.

That’s not an environment that will suit Porcello. His 1.62 HR/9 is the eighth-highest home run rate among qualified major league starters, per FanGraphs. This is hardly a new concern for Porcello, who posted a similar 1.68 HR/9 rate in 2017 when he led the majors with 38 home runs allowed.

If anything, Porcello is fortunate that he hasn’t allowed more home runs. Considered a groundball pitcher early in his career, Porcello has drastically altered his approach over the last few years. His groundball rate has sunk to a career-low 37.6% and his 43.1% Fly ball rate is the fifth-highest in the majors. His 12.7% HR/FB rate is a bit below league average and easily the best he’s posted since joining the Red Sox outside of his outlier Cy Young campaign.

So, Porcello has become an extreme fly ball pitcher yet those fly balls are leaving the park at a lower rate. His 10.2% Infield Fly rate is about normal for his career and only slightly better than league average, indicating he hasn’t suddenly developed a knack for inducing weak pop-ups to explain his declining HR/FB rate. He’s also allowing a ton of hard contact. Per Baseball Savant, Porcello’s 167 Hard Hit Balls (95+ mph exit velocity) are the 16th most in the majors.

As bad as his season has been, it would be far worse with a normalized HR/FB rate that benefits from Fenway ranking in the bottom third of MLB parks for home runs.

Porcello has been at his best at Fenway this season. He hasn’t been good, just better than on the road. He owns a 6.27 ERA on the road this season and is allowing a .313 batting average to opposing hitters.

The right-hander’s 4.09 ERA in August may suggest he’s showing signs of improvement but this is fools gold. This figure is heavily influenced by a pair of six-inning, one run efforts against the lowly Baltimore Orioles and Kansas City Royals. Porcello lasted only five innings in his last outing, giving up three runs while issuing four walks. He was blasted for five runs over five innings in his only other start this month.