If the right-handed first-baseman battle is unique among the Yankees’ three spring-training position battles because it’s the only one that features a head-to-head competition, the battle for fifth starter is unique because it’s the only one that has a clear favorite entering camp. Well, maybe “favorite” isn’t the right term to use. This is Crash Pavano we’re talking about, after all.

The top four spots in the Yankee rotation are set with Chien-Ming Wang, Mike Mussina, Andy Pettitte, and Kei Igaway. If Mr. Glass is able to pitch with any level of effectiveness during spring training and manages to make it to Opening Day without slamming his finger in a door or cutting himself shaving, he’ll be the fifth starter. Not that the odds are very good of that happening, or that there’s much chance of him finishing the season with that job. If Pavano pitches well through April and May it’s almost a lock that he’ll be traded in June. The only variable there is the health of the rest of the rotation.

So while the fifth starter job is Pavano’s to lose, the competition in spring training will be no less compelling as a result. Here’s a quick look at the combatants:

The above chart does not include Tyler Clippard or the two starters obtained in the Randy Johnson trade, Russ Ohlendorf and Steven Jackson, because none of those three have thrown a single pitch above double-A. Of course, the same is true of Philip Hughes, who is far and away the best pitcher listed above. But then there are limits on Hughes’ participation here as well.

Soreness in his pitching shoulder limited Hughes to 86 1/3 innings in his first full professional season in 2005. Last year, the Yankees cautiously held the 20-year-old to 146 innings. This year his innings cap will be 180. If Hughes were to make the Yankees out of camp, the Yankees would have to keep Hughes on short leash in order to keep him from exceeding that total over the course of a full season. Last year Chien-Ming Wang and Randy Johnson lead the Yankees with 33 regular season starts. Spread across 33 games, 180 innings averages out to just 5.45 innings per game, and that doesn’t include potential postseason starts, which would consume the innings the Yankees might be able to save by skipping Hughes’ turn on the few occasions when scheduled off-days allow them to do so.

The Yankees are to be commended for their careful handling of Hughes. They’re doing all the right things regarding his workloads, and their impulse to have him start this season at triple-A is also a good one. True, Hughes could likely pitch effectively in the major leagues without a stint in triple-A, but there’s no harm in easing him into things. Starting him out in Scranton is an excellent way for them to insure that he won’t be extended beyond those 180 innings. Another is to using him sparingly out of the major league pen in the early months of the season as the Twins did with Francisco Liriano last year.

Let’s crunch some numbers here using 2006 AL innings-pitched and ERA leader Johan Santana and complete games leader C.C. Sabathia as examples of the best and most durable American League pitchers. Both Santana and Sabathia averaged about 6.88 innings pitched per start last year. Assuming , then, that Hughes will average no more than 6 2/3 innings per major league start, he could make 27 starts for the Yankees in 2007 before exceeding his limit. Of course, when you factor in a full postseason run, the Yankees could require close to 40 starts from their best pitchers, which leaves Hughes inactive for significant chunks of the season. There are three possible alternatives to simply letting Hughes pitch until he hits 180 innings and thus facing the heat of the pennant race and postseason without him.

If the Yankees let Hughes pitch on a strict innings limit in triple-A for the first couple of months of the season, then promote him in June they might only get 19 major league starts out of him between the regular and postseasons, but they’ll keep him active throughout the season. If the Yankees skip the fifth spot in the rotation every time the schedule allows them to in April and May, they’ll first need a fifth starter in June on the fifth of the month. To put Hughes on schedule for that start, the Yankees could make him the fifth man in the Scranton rotation. That would give him 11 starts in triple-A before his major league debut on June 5. If they then skip Hughes’ turn in the major league rotation whenever the scheduled off-days allow them to do so over the remainder of the season, Hughes would make 16 major league starts during the 2007 regular season. If they limit him to five innings in each of his 11 triple-A starts but otherwise let him loose in the majors (again assuming a maximum 6 2/3 innings pitched per start), he would finish the regular season with a maximum of 161 2/3 innings pitched between Scranton and New York. That would then allow him to make three postseason starts (say one in the ALDS and two in the ALCS) without meaningfully exceeding his 180-inning limit. If all of that goes according to plan and the Yankees find themselves in the World Series, I’m sure an extra two starts in pursuit of a World Championship would be perfectly acceptable.

Alternately, the Yankees could limit Hughes to side sessions in April, promote him directly to the major league rotation when the fifth spot comes due on May 5, and again skip his turn whenever the schedule allows. That would result in 24 major league starts in the regular season and a maximum of 160 innings pitched prior to the postseason.

A third option, and the one that I think would ultimately be most beneficial to both the team’s goals for 2007 and Hughes’ long term development, would be to pitch Hughes in regular rotation in the major leagues beginning on June 5 (that is not skipping his turn when off-days allow). That would result in 21 regular season major league starts totalling a maximum of 140 innings. That leaves 20 extra innings which Hughes could pitch out of the pen in April and May (or, alternately, four minor league starts with a five-inning limit, or even five minor league starts with a four-inning limit). Again, that would result in 160 regular season innings and leave him free to make three postseason starts within his 180-innings limit with the possibility of two more World Series starts if needed beyond that limit.

Each of those three scenarios assumes a level of success for both Hughes and the team that is not a foregone conclusion, but even in these best-case scenarios it’s clear that Hughes can’t be used as the fifth starter in April, and likely not in May either lest he be shut down in advance of the playoffs and possibly even before the divisional race is decided. The Yankees will need a fifth starter three times in April and four more times in May. If Pavano gets a splinter, the Yankees will need someone other than Hughes to take those turns. Even if Pavano is able to take the ball each time, the Yankees will need to use spring training to decide who they’ll turn to should the rotation spring a leak elsewhere.

Having reduced the candidates to Karstens, Rasner, and Sanchez, I’m going to further cull the field by eliminating Sanchez. Sanchez didn’t hit triple-A until the middle of last year and made just nine starts at that level before being shut down with tenderness in his pitching elbow. A highly touted prospect in his own right, though certainly not in Hughes’ class, Sanchez should also be handled with kid gloves this year in the hope that he can establish himself in triple-A, stay healthy, and emerge as a candidate for the 2008 rotation or, in a best-case scenario, down the stretch this year.

That leaves Karstens and Rasner, the two rotation patches that the Yankees used late last season. Although Karstens is the more familiar face due to his having made six starts last year to Rasner’s three, I’ve always been partial to Rasner. The stats above show why. While both men where rather fortunate on balls in play last year, Karstens was both more fortunate and significantly less likely to record a strikeout, a scary combination that could lead to a huge increase in hits and thus runs allowed this year. What’s more, Karstens has come by his nickname “Scary Fly Ball Guy” (props to Steven Goldman) honestly. Consider the home run rates above. Then consider that Karstens groundball-to-flyball rate last year was 0.67. While that came in a small sample, only one of the 80 major league pitchers who qualified for the ERA title last year had a more extreme fly-ball rate. By comparison, Rasner’s groundball-to-flyball rate, in an admittedly even smaller sample, was 1.13, which would have ranked him a more respectable 51st out of those 80 qualifiers. Karsten edges Rasner in the important category of minor league K/BB ratio, but Rasner edged Karstens in nearly every peripheral stat you can dig up from their major league stints last year and, frankly, I was more impressed with Rasner’s stuff and composure after seeing them both pitch last September. Still, just as Pavano would be keeping the fifth starter spot warm for Hughes, Rasner or Karstens will hopefully be doing no more than that. While Rasner may be a perfectly viable fifth starter, he’d be a significant downgrade from what’s expected of Wang, Moose, Pettitte, or Igawa, and the rest of the cookies Cashman collected this winter still need to bake a bit longer.