Derek Jeter and the Curse of Age

He’ll get his batting average up a bit — but only to .264, slightly worse than his career low of .270 last year. His on-base percentage, however, will be a more respectable .340.

He’ll steal 13 bases (he has none so far), the 16th consecutive season in which he finishes in double digits in that category. But he’ll wind up with just six home runs, breaking a similar streak.

He’ll play in 131 games, meaning that he’ll probably endure a stint on the disabled list. He’ll score 59 runs and have 51 r.b.i., both career lows.

Yankee fans might think this sounds unduly pessimistic; Jeter got off to an even worse start last year before rebounding somewhat. But history suggests that his struggles are not unusual; elite players are often average ones by the time they reach his age.

So how did I reach this conclusion?

I simply averaged the statistics that Hall of Fame shortstops compiled when they were 37, the age that Jeter will turn next month.

(A few qualifications: Because Luke Appling, the Chicago White Sox great, was serving his country in World War II when he was 37, I used his numbers from his age-36 season instead. And the averages do not include the seven Hall of Fame shortstops who were already retired by the time they were 37.)

There are good reasons why Jeter is still a major-league shortstop at his age. He was among the best players in baseball at his peak. He’s an outstanding athlete, and has a well-rounded set of skills. He’s rarely been injured. All of these things correlate with longevity.

Some shortstops were still elite players at age 37. Ozzie Smith hit .295, stole 43 bases and won his 13th Gold Glove. Honus Wagner was an M.V.P. candidate, compiling a .423 on-base percentage. Appling, in the year before he went off to serve in the war, hit .328. Ernie Banks hit 32 home runs as a 37-year-old in 1968, although he was no longer playing shortstop.

But some greats, like Lou Boudreau and Arky Vaughan, were already retired by the time they were 37. Others, like Phil Rizzuto and Joe Cronin, had become bench players.

And some who continued to play were not very effective. Luis Aparicio hit .232 when he was 37. George Davis hit .217. Just two Hall of Fame shortstops — Banks and Cal Ripken — hit has many as 10 home runs. None scored more than 87 runs or had more than 89 r.b.i.

Jeter’s decline, then, is in some sense quite typical. Most great shortstops, if they had any power to begin with, had lost most of it by the time they were 37. Some were nevertheless able to contribute significant value to their teams by continuing to leg out base hits, hit a few doubles, run the bases well and draw walks — but others were not.

Whether Jeter can continue helping the Yankees to win ballgames will depend on those things. (His power, because he hits so many ground balls, is almost certainly not coming back.) We are long past the golden age of shortstops, when Jeter, Nomar Garciaparra, Alex Rodriguez and Miguel Tejada were M.V.P. candidates every season. Instead, the average American League shortstop is hitting just .245 so far this year. The threshold is not all that high for Jeter to remain a viable option for the Yankees, and it is too soon to pull the plug.

But there probably will not be any miracles, either. Bill James, the influential baseball writer and statistician, found years ago that the typical baseball player peaks at age 27, and his decline begins to accelerate at roughly age 32. Any shortstop who has survived in the majors to age 37 has already defied the odds.

Some hold it together for a few years more than others, but the decline comes sooner or later. Baseball players can be thankful, at least, that their careers tend to end with a whimper — and not, like a Brett Favre concussion blow, with a bang.