Greetings, Beyond the Box Score!  My name is Jesse, and I also write for the Twins over at the SB Nation site Twinkie Town.  For my first post I'm going right to the well, and hitting up my favorite player of baseball's modern era:  Ken Griffey Jr.

Entering his twentieth season, Ken Griffey Jr. is 38 years old.  It's bizarre to realize that baseball's Golden Boy is nearing the end of his career.  Sure, he can play another few years--he can play as long as he wants.  But it's strange knowing that sooner rather than later, those numbers that at one time were skyrocketing at astronomical proportions will cease to climb.  How much longer can The Kid continue his quest for baseball immortality?

At least through his age-38 season.  By the time most baseball players reach their 38th birthday, they're well into the stages of decline (if they're playing at all).  On Junior's 38th birthday he was prepping for Thanksgiving, and we already know he doesn't fall into the "most baseball players" category.  Beyond that it's pure speculation, but PECOTA projects Griffey will play through 2011 before leaving the game.  Let's browse through a handful of his career comps to see how they fared.

Paul O'Neill, 2001

O'Neill's last season was in 2001, and was still a solid offensive contributor.  He's no Junior, but the fact that he was able to maintain his productivity is a good sign.

Fred McGriff, 2002

This was McGriff's last productive season, posting an 125 OPS+.  Fred isn't going to make the Hall of Fame, but is a great candidate for the Hall of Very Good for a Very Long Time.  While he regressed from '01 to '02, he was still a dangerous bat to have in the lineup.  If Griffey could replicate McGriff's line above, it would be a good year.

Cliff Johnson, 1986

Johnson was never a star, but he was usually an efficient hitter. Even in his final season, at age 38, he posted a .110 OPS+ and a very reasonable .274 EQA.  A year like this would be disappointing for Griffey, as a steep decline in power like this would signal an end to his career closer to 2008 than PECOTA's anticipated 2011.

Luis Gonzales, 2006

Gonzales had a nice, slow decline in his numbers going on prior to his injury-truncated 2007 campaign.  His numbers in '06 certainly weren't bad for a 38-year old, and he racked up a ridiculous number of doubles.  He's still playing (with the Marlins this season), giving more credibility to the belief that Junior can play when he's 40.  Griffey putting up a line like this would, again, signal a drastic power and significant on-base skill reduction; but it does prove that players at age-38 can remain as relatively productive as they had been at age-37.

Larry Walker, 2005

Once again we're looking at a player who was out of baseball following his age-38 campaign.  Walker's last couple of seasons were littered with minor scrapes and days off, something Griffey could identify with, but he remained a force to be reckoned with when in the lineup.  An OPS+ of 130 at this stage of anyone's career is impressive.

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Generally, there are two types of position players who are still heavily involved in the game at the age of 38:  potential Hall of Famers, and scrappy infielders who have been able to find a job due more to versatility and a lack of better options than their own talents (you tell me how Jeff Reboulet played until he was 39).  We know which one of those Griffey is, but again this isn't about how great he's been historically; it's about how long he can continue to grace our summer.

Baseballreference.com does something similar to PECOTA, in that they generate a couple of comparative lists.  For comparative purposes, let's see what age each of the players on those lists played to.

Similar Batters:  Sammy Sosa (39, still active); Gary Sheffield (39, still active); Mickey Mantle (36); Mike Schmidt (39); Jeff Bagwell (37); Fred McGriff (40); Willie Stargell (42); Frank Thomas (40, still active); Eddie Mathews (36); Reggie Jackson (41)

Most Similar By Age:  20-22, Al Kaline (39); 23, 24, Mickey Mantle; 25-32 (36), Frank Robinson; 33-36 (40), Sammy Sosa (39, still active)

While all these players have greatness in common, not all of them were necessarily productive at the tails of their careers.  It's a truth in baseball as it's a truth in life:  when you get to a certain age, performance suffers.  How and when are the questions that matter, and things come to an end even for the historically magnificent.  They even will come to an end for a player with one of baseball's sweetest swings ever.

A select few can continue to take productive plate appearances, even into their late 30's and sometimes even into their 40's.  We know that if Junior can keep himself off the disabled list, he'll be able to play into his 40's if he so chooses.  It's at this point in his career where productivity and the decision to remain active in the game go hand-in-hand, and it becomes a precarious dance to see if the numbers continue to justify his playing time.

PECOTA projects Griffey's weighted mean at .268/.350.481 in 435 plate appearances.  While I want to be more optimistic than this, it's a very reasonable forecast.  Over the last couple seasons Griffey's been hitting fewer line drives, more pop-ups and is in a decline with his home run rates.  Last season only 13.2% of his fly balls were home runs, which is only a hair above average.  If these peripherals continue to decline at this rate, PECOTA's projection of Griffey playing through 2011 may actually be optimistic.

In any era of baseball it's been common to see great players continue on into their 40's; it's often expected.  But no matter what happens to him health-wise, his numbers will continue their ebb.  All we can hope for is one more ball, one more home run, one more season.

My projection:  4 more years, 92 more home runs, 479 more hits.