Last week I noted that Nate Silver expanded upon Bill James’ initial work on aging patterns to show that hitters tend to peak between ages 25 and 29, cresting at 26 and 27, with some understandable variations by position. Speed-based players like middle infielders and center fielders peak toward the earlier side of that range, while catchers develop more slowly, and third basemen, who tend to be slower and thicker, peak later and retain a larger share of their value over a longer period of time.

Nate’s findings mesh with another concept that James introduced to the masses in the 1982 Baseball Abstract, the existence of a defensive spectrum which runs like so:


The positions at the left end of the spectrum are easier to defend, but carry higher offensive demands, while the positions to the right prioritize defensive skill over hitting ability. Note how well the 2008 Equivalent Averages by position match up with that spectrum:

Pos   EqA
1B   .283
LF   .276
RF   .276
3B   .270
CF   .268
2B   .264
SS   .255
 C   .252

As players age, they tend to drift to the left side of the spectrum; many a superstar was drafted out of high school or college as a shortstop, only to gravitate to a less challenging position as his body filled out and he developed as a hitter. Gary Sheffield-stormy career and all-is a prime example. Drafted as a shortstop, he moved to third base during his second year in the majors, then to right field in his sixth, and these days he’s playing out the string as a DH. Attempts to move players to the right rarely work out as well. We have yet to reach the Ides of March, and already the Cardinals‘ attempt to convert outfielder Skip Schumaker to second base appear headed for oblivion.

Figuring out when to move a player to a different position is a tricky business. Prospects are often shifted before reaching the majors, either based upon the needs of their clubs, the desire to expand their defensive utility, or, particularly with catchers, to maximize their offensive potentials and lengthen their careers. Down the road, older players are often shifted after losing a step in the field; 10-time Gold Glove-winning center fielder Ken Griffey Jr. became a corner outfielder at 37.

Quantifying the long-term impact of moves is rarely possible, but here’s a look at some of the factors in play regarding potential position shifts that have been proposed:

Chase Utley, Phillies 2B

Recently, colleague Steven Goldman observed that “the 30s are rarely kind to second basemen.” Utley, who is coming off of surgery to repair a torn hip labrum, passed that milestone back in December. It remains to be seen whether his typically outstanding defense (+19 FRAA last year) suffers in the short term, or if the injury could mark the beginning of a more typical large-scale decline. If the latter is the case, he’s got plenty of headroom to withstand a position shift given last year’s .311 EqA and a career mark of .304. Acknowledging the presence of first baseman Ryan Howard, right fielder Jayson Werth (second on the team last year with a .301 EqA ), and left fielder Raul Ibanez (signed to a three-year deal this winter), third base would seem to provide the easiest out, but the hot corner is no picnic either, and the move is out of the question this year.

Victor Martinez, Indians C

Never known for his defense, Martinez improved his success in nabbing would-be base thieves in recent years while also dabbling at first base to keep his potent bat (career .295 EqA) in the lineup. Hamstring and elbow injuries limited him to just 73 games, two homers, and a .260 EqA last year, though backup Kelly Shoppach‘s .301 EqA and 21 homers in 403 plate appearances provided a silver lining. PECOTA sees the 30-year-old Martinez and place-holding first baseman Ryan Garko as equal offensively, forecasting both for .266 EqAs this year. That’s substandard for the position, but Martinez’s strong track record suggests that he could exceed that forecast given less time behind the plate, thus keeping Shoppach’s bat and glove in the lineup. Expect to see Martinez starting at least 25 percent of the Tribe’s games at first, though he may not be the only potential position-shifter vying for at-bats there. Power-hitting prospect Matt LaPorta (the key swag from the CC Sabathia deal), is the longer-term candidate, but he’s currently marking time in left field, the position he assumed only after being drafted. He’s progressed from inevitable comparisons to Ron Kittle (whom James called “worst young outfielder I have seen since Greg Luzinski“) to the point of serviceability, but his lack of range inevitably tickets him for first base.

Chipper Jones, Braves 3B

The 37-year-old Jones presents a quandary for the Braves, ranking as one of the games’ most irreplaceable players, but one who frequently needs replacing nonetheless. He’s batted .342/.435/.592 over the past three years, while averaging just 124 games per season due to injuries. Never a stellar third baseman (though our new play-by-play defensive metrics hold him in much higher regard than our older system), he’s resisted a move off of the hot corner ever since returning from a left field sabbatical that ran from 2002 to mid-June of 2004. In a vacuum, a move to first would make sense, but the Braves have nobody ready to take over at third, and they’re still trying to salvage the acquisition of underpowered Casey Kotchman from the Angels in the Mark Teixeira deal. This one’s not going to happen anytime soon.

Jeff Clement, Mariners C

Former Mariners GM Bill Bavasi didn’t become the architect of baseball’s first 100-loss team to exceed $100 million in payroll by making moves that made sense. Even with Clement considered one of the organization’s top two prospects entering 2007 and 2008, Bavasi re-signed starting catcher Kenji Johjima to a three-year, $24 million extension in April 2008 while ignoring the 32-year-old’s potential for decline. Johjima’s EqA crashed from .272 in 2007 to .229 last year, but he still started about three times as many games as the 24-year-old Clement, who himself struggled to a .234 EqA while splitting time at catcher and DH. PECOTA foresees a string of .280-ish EqAs in Clement’s future, but dislikes his defense enough to suggest he’ll cost more than one win a year behind the plate, echoing the sentiments of scouts never sold on his throwing ability. Throw in a recent knee surgery, and a move to first base or DH appears academic, though the presence of both Russell Branyan and Griffey-like Clement, both lefties-are blocking the way.

Joe Mather, Cardinals OF

As the potential shift of Schumaker attests, the Cardinals aren’t afraid to employ surplus outfielders elsewhere on the diamond. With Troy Glaus shelved for April, they’ve got a hole at third base, and they’re currently auditioning the late-blooming Mather, a 26-year-old corner outfielder who played third in college but hasn’t seen regular duty there since 2004. Mather’s PECOTA forecast for this year calls for a .265 EqA, with a high of .273 down the road-a level of productivity better suited to the hot corner. Reports out of the Cardinals’ camp suggest he’s already sewn up the Opening Day spot, and his newfound versatility enhances his chances of sticking around once Glaus returns.