Growing pains: All pitchers go through adjustment period

What the Yankees are doing right now, really, is a risky proposition.

Take a look at their rotation; 40 percent of it is young and inexperienced. To put it into statistical terms, Phil Hughes and Ian Kennedy are a combined 44, only 5 years older than Mike Mussina. When "Moose" took the mound for his first career start on Aug. 4, 1991, Hughes was just 5 years old, Kennedy 6.

By the way, that fails to account for Hank Steinbrenner's desire for Joba Chamberlain, 22, to join the rotation. If Hank prepares his own set of "Joba Rules," then potentially three-fifths of the Yankees' rotation would be 23 or younger.

Should it be any surprise, then, that through three weeks and two days of the season, Hughes and Kennedy are a combined 0-5 with a 9.20 ERA and 2.21 WHIP?

Sorry Hank, Brian Cashman, Joe Girardi et al, but history should've cautioned you against entering the season with so many young arms in high-profile roles. Pitchers -- even the best -- take time to get acclimated to big league competition.

Don't believe me? Consider that Jake Peavy kicked off his career 14-15 with a 4.61 ERA in his first 38 starts. Johan Santana had a ghastly 6.49 ERA and 1.81 WHIP in 86 innings in his rookie year. Even Brandon Webb had a 15-start stretch early in his career (in 2003-04) when he was 3-7 with a 4.64 ERA and 1.43 WHIP.

So, I'll repeat: Every pitcher hits an adjustment period.

The question, then, becomes, how long is that proverbial "adjustment period"? Can Hughes or Kennedy owners afford to wait on them much longer?

To find the answer, I collected start-by-start data of some of the most promising prospects in baseball from 1996 to 2005, a 10-year span. Why 1996-2005, instead of 1998-2007? Simple: Many top prospects from 2006-07 have yet to reach the majors, and those who have haven't been around long enough to provide much career data. Prospects included were all pitchers who earned a top-50 ranking by Baseball America in any one season from 1996 to 2005, a fair cutoff point since Kennedy, considered the lesser of the two Yankees youngsters, placed 45th on BBA's list this season.

Some interesting facts about the group:
• 147 pitchers made the cut.
• 115 of them have made at least one MLB start.
• Four more are career relievers on active MLB rosters.
• Of the 115 to start once, 44 went on to make at least 100 MLB starts.
• Seventeen others are active members of MLB rotations who have yet to reach 100 starts.
• Twenty-one of the 44 with 100-plus starts remain in current MLB rotations.
• Of the aforementioned 115, 10 are now relievers on active MLB rosters.
• One of the 115 is now an outfielder (Rick Ankiel).

That means of the 115 prospects who reached the majors, 38.3 percent went on to make at least 100 starts, and that number could rise to 53.0 if the rest of the active arms get there. That's a pretty good success rate, and bodes well for Hughes and Kennedy owners. Of course, the rest of the data, when broken down by career start in the chart below, indicates it might bode well only for the duo's keeper-league owners:

A couple of notes: "QS%" represents quality-start percentage. "OS%," meanwhile, is "outstanding-start" percentage, which operates under the same idea, only that I define an "outstanding start" as eight innings or more, and one earned run or fewer. "Wpct," obviously, is winning percentage, and I've also included "IP/GS" to demonstrate how deep these pitchers were working into games at these stages of their careers.

Most interesting is that pitchers generally tended to be pretty effective in their first career start, though they lasted almost a full inning less in their first starts than pitchers approaching their 100th. I'll attribute that effectiveness to the "unknown" factor; opposing hitters are least familiar with a pitcher's arsenal the first time they see him. So, if you're the gambling type and like matchups, have less fear of a pitcher's first start than, say, his 10th.

But what the chart above also proves is that it takes about 40 big league starts before a pitcher, on average, tends to hit his groove. Note the significant improvements in ERA, WHIP and innings per start of pitchers making their 41st through 50th starts compared to those in the 31-40 range. In other words, if you're banking on Hughes, who has 17 starts under his belt, you might be waiting until late August or September for him to hit his peak, assuming he sticks to those historical trends. Kennedy owners, sorry to break this to you, but you might be waiting a lot longer; he has six career starts.

So, if you're in the bargain-hunting frame of mind, here's a gander at some of the pitchers either approaching or now in that golden "career start No. 41-50" range: Edwin Jackson (50), Tom Gorzelanny (48), Shaun Marcum (43), Chad Billingsley (39), Joe Saunders (37), Brian Bannister (37), Adam Wainwright (36), Matt Chico (36), Gavin Floyd (32), Jon Lester (31), Micah Owings (31) and John Danks (30).

Conversely, the following pitchers, based on their number of career starts, might struggle with adjustment periods for significant portions of 2008: Kyle Kendrick (24), Kason Gabbard (23), Jesse Litsch (23), Ubaldo Jimenez (20), Mike Pelfrey (20), Andrew Miller (17), Jair Jurrjens (11), Franklin Morales (11), John Lannan (9) and Manny Parra (5).

Perhaps the Yankees' focus on youth indeed will pay off with another World Series title … but if history is any indication, don't count on it before 2009.

Tristan H. Cockcroft covers fantasy sports for ESPN.com. You can e-mail him here.