Who Will Buchholz Be in 2015?

What does Boston's erstwhile ace have in store for 2015? (NESN)

Of all the questions the Red Sox have going into 2015--how will Hanley Ramirez handle playing the outfield? How will Rusney Castillo perform in his first full major league season? How much will Xander Bogaerts improve?--perhaps none is harder to answer than how effective will Clay Buchholz be?

Buchholz, after all, is 30 years old, coming off knee surgery and a terrible season in which he was worth 1.6 wins below replacement. The year before that, he missed three months and still ran out of gas in October as Boston streaked towards another championship. The year before that, he had a 5.53 ERA at the All-Star Break and only started to pitch well after Boston's season went in the tank.

Will Buchholz be the ace that he has been at times in the past? Probably not. Aside from a stellar first half in 2013 and a fluky 2010, the two-time All-Star belongs in the middle of a rotation more than the top.

Still, it bears mentioning that in 2014, Buchholz didn't pitch nearly as poorly as his 5.34 ERA suggests. In fact, his strikeout rate was right in line with his career rate (a smidge better, actually), his walk rate was half a batter lower per nine innings than his career rate, and his 2.44 K/BB ratio was significantly better than his 1.99 career ratio coming into the season. His home run rate was a near perfect match for his career mark and his batted ball distribution was about the same as it usually is.

So if Buchholz pitched as well as he normally does, then why did he end up with such terrible results?

For starters, he was unlucky on balls in play with a .315 BABiP that was 30 points higher than his career mark. It was the second-highest mark of his career and, not surprisingly, resulted in the second-highest hit rate of his career, which led to the second-highest WHIP of his career. He was also terribly unlucky with strand rate, with the worst LOB% in baseball. Buchholz's ERA should have been at least a run lower, as his FIP, xFIP, and SIERA were all barely above four.

Mere regression to the mean should make Buchholz a much better pitcher in 2015, at least league average if not better. The same could be said about a lot of Red Sox who underperformed last year, but for Buchholz it holds especially true.

Even more challenging than figuring out how Buchholz will pitch is trying to determining how often he will pitch. The polar opposite of sturdy former teammate Jon Lester, Buchholz is notoriously fragile and has earned a reputation in Boston for being soft, a guy who won't take the mound unless he's 100 percent healthy (Jacoby Ellsbury, somewhat unfairly, had a similar reputation). Eight years into his career, he's still yet to make 30 starts or complete 190 innings in a season. Even more troubling is that he's never made 17 starts in back-to-back years. The question isn't if he will miss time, but how much?

The Red Sox have to hope it's just a handful of starts, if only because their fortunes have closely mirrored those of Buchholz. The team folded when he got hurt in 2011, and stunk when he stunk in 2012. They won the World Series when he had a Cy Young-caliber half in 2013, then bottomed out again when he faltered the year after. For better or worse, as Buchholz goes, so go the Red Sox.

And as one of the team's five starting pitchers, Buchholz is an incredibly important piece. If he regains his form, Boston probably will too. But if he has another crappy season, then it's going to be much harder for the Sox to succeed in spite of him, especially if they don't have an ace who can pick up the slack.