When the Tigers announced that Phil Coke would be a member of the teams starting rotation following the 2010 season, I was skeptical. Coke had worked primarily as the stereotypical fastball/slider reliever during his time with the Yankees before mixing in his changeup last year when he was traded to Detroit and it was effective enough (1.40R/C - runs above average/100 pitches).
Still, the thought of moving someone who had worked largely with the platoon split - while showing a significant platoon split - to the rotation seemed risky. Coke posted a 32K/8BB ratio in 28.2 innings vs lefties last year, but had a 21K/18BB ratio in 36.0 innings vs righties, which should've let anyone paying attention know that he would struggle mightily in the rotation, where he can't be protected from seeing twice as many right handers as left handers.
In the bullpen last year, Coke posted a strong 3.23 FIP, but a .335 BABIP pushed his ERA up to 3.76. But with his move to the rotation, his strikeout rate has plummeted from 7.38 to 4.32 and though he's remained one of the most HR lucky pitchers in baseball with a miniscule 2.9 HR/FB% his ERA after a final ugly start is a ghastly 4.91.
In response to Coke's recent struggles (he's allowed 16ER in his past three starts, totaling 13.2IP) the Tigers have decided to give lefty Charlie Furbush a chance to start instead. In profiling Furbush I noted that he has a bevy of capable MLB offerings, but lacked a true put-away pitch. His slider and curveball have proven effective against left handers, but like Coke, he's shown a significant platoon split with a 2.11 FIP against lefties and a 6.77 against righties.
Of all of Furbush's off-speed options, I think his changeup shows the most promise, along with offering the best potential as a viable option against - but it's also the pitch he's shown the least faith in, throwing it just 4.1% of the time. If Furbush, who's 3/4 slot will give righties a very good look at his off-speed offerings is going to survive in the rotation on a long-term basis, he'll need to show both a good feel for, and a greater faith in that changeup.
My intent here isn't to suggest that Furbush can't be an effective starter - at least for awhile - but on a long term basis, he isn't likely to be anything more than a back-end arm if he continues to operate as is. If he can't find that effective method for dealing with right handers, the Tigers will essentially be swapping one under-tooled left-handed option for the next.
And that's not a solution.