I was all set to write a post about how the Yankees’ season hinges on pitching, but Rob Neyer apparently beat me to it. Well, tough luck, Rob. I’m writing mine anyway.

Earlier today, David Pinto released his New York Yankees Rotation Evaluation. Using the Marcel Projections, Pinto estimates that the Yanks’ top five starters — omitted the bound-for-the-bullpen Joba Chamberlain — will pull down an ERA of around 4.14 in 689 innings.

This is of course wildly optimistic and leaves a lot of starting pitching innings to be filled by hurlers who are not one of the Yanks’ top five pitchers. It also relies on the assumption that Mike Mussina will throw to a 4.59 ERA, an improvement approximately 0.66 runs over his 2007 effort. Stranger things have happened.

And here is where Rob Neyer takes over. After reading Pinto’s post, he and I had the same idea. Take it away, Rob:

Aside from Pettitte and Wang both being good, though, I find it essentially impossible to predict what’s going to happen here. In fact, that’s my prediction: Every prediction will fail. Too many moving parts. Between Mussina’s recent struggles and the young starters’ lack of experience and non-history of durability, how can anyone know, really?

…For all the talk about the Yankees’ six starters, would anybody like to bet they’ll get by with only six? Last year nine Yankees started more than five games. The year before that, seven; the year before that, nine. We may guess that in addition to the six guys we’ve heard so much about, at least two others will play significant roles in the rotation.

The Yankees have done a real good job of accumulating talent. They’ve got six starting pitchers who have demonstrated — some for many years, some for a few months — abilities that sometimes lead to Hall of Fame careers. But if the Yankees wind up winning 95 games (again), we’ll look back with admiration for Joe Girardi and Brian Cashman‘s ability to take advantage of all those talents through six months of twists and turns and sprains and tender elbows.

Neyer, of course, nails this analysis. But beyond Neyer’s “twists and turns and sprains and tender elbows” comes the fact of Major League life for young pitchers: the specter of inconsistency. While Phil Hughes struggled with a return to form last year following his leg injuries, he’s been utterly dominant this Spring. Meanwhile, in their brief Major League careers, Joba Chamberlain and Ian Kennedy have yet to falter.

But they will, and it won’t portend the end of the world. We’ve seen it during Spring Training, a fine time indeed to see struggles. While Phil has been mowing them down and reminding everyone, albeit in limited time, why the organization has long loved his stuff, Joba and IPK had rough early outings followed by better second outings. The two will only get stronger as time wears on, but at some point during the season, they will turn in clunkers.

It is quite possible that the Yanks end up with two candidates for Rookie of the Year in 2008. Joba and Kennedy could be battling out with Evan Longoria when September rolls around. But can the Yanks at the same time expect perfection each outing? No, and that’s why predictions are dicey.

In the end, the kids will be all right, and for years to come, they should remain that way. But Yankee success in 2008 will depend entirely on the consistency of the pitching. In baseball, this is always true, but with three young guns on the way up, this lesson will be on display for all to see. It will be a great ride, but it could get a little bumpy. Now, let’s just get to Opening Day all ready.