Boston Dirt Dogs photo illustration

Ah, May 15. That day of universal celebration across Red Sox Nation: Josh Beckett's birthday. On this merry occasion, Beckett's mailbox will surely be stuffed with the most fervent wishes of well-being from his legions of adoring fans. And he'll even be returning the favor, toeing the rubber this afternoon against the Seattle Mariners and doubtless delivering a gift of a performance to his supporters -- all 15 of them.

Sarcasm aside, Red Sox fans have unfortunately been led to expect next to nothing from Beckett, given his last few months in the spotlight. He has supplemented subpar performances on the mound by being at the center of nearly all the negative PR currently surrounding the team. For some reason, an ERA hovering around six doesn't put people in a forgiving mood.

But Beckett's struggles on the field shouldn't be attributed to the deteriorating clubhouse environment he has helped to create; plenty of malcontents have been consistently great players, and his attitude doesn't affect the jump on his fastball. What should be more alarming for the Sox is the fading strength of Beckett's 32-year-old right arm.

Beckett's velocity topped out in 2006, his first season with the Red Sox. His fastball averaged 94.7 mph, and he relied on the pitch heavily, throwing it 69 percent of the time. Between '06 and '09, his velocity remained relatively constant, but he began utilizing his peripheral pitches more frequently, throwing his curveball and changeup more often and even mixing in a cut fastball. He was one of the most productive pitchers in baseball over this period, ranking 12th among all hurlers in Wins Above Replacement.

In 2010, Beckett turned 30 -- bad news for any athlete, pitchers included. A study on peak age for pitchers conducted by Tom Tango found that, on average, the number of innings pitched for all pitchers tops out at age 27. Pitchers' value (measured in WAR per game) continues to increase until it crests at age 30, due to the inability of below-average pitchers to remain in the league beyond their mid-20s physical peaks; in other words, only good pitchers are able to stay in the majors into their 30s. Even so, as Tango writes, pitchers "are definitely on the down slope starting at age 30."

Beckett appears to be no exception to this trend. Since turning 30 in May of 2010, he has lost about three MPH off both his fastball and curveball, suggesting his arm just doesn't have the life it once did (all data courtesy of Fangraphs).

Things have only gotten worse in 2012. Beckett has thrown his fastball at 91.5 mph, on average, and he seems to have recognized the relative weakness of the pitch; he has thrown it at a career-low rate of 49.7 percent during the young season. To compensate, Beckett has added a much higher proportion of cutters and changeups, which seems to be a sensible adjustment for an older pitcher -- except that, so far, it hasn't really worked, as evidenced by the results he's gotten on the field.

Within this context, his mostly exceptional 2011 begins to look more like an aberration. He was the beneficiary of luck and good timing for much of last year; he allowed a career-low .245 BABIP -- which may have had something to do with his new, more deception-based approach -- and stranded a career-best 80 percent of runners he allowed on base.

But it's still too early to pass any definitive judgment. We'll need to see more of a healthy Beckett in 2012 to determine whether the sudden drop in velocity is due to a pesky lat or a significant decrease in ability. Perhaps he can recapture some of the 2011 magic by pitching smarter, not harder.

The bottom line? Beckett will have to reinvent himself a lot more successfully than he's done early in 2012 if he hopes to be in Boston for much longer -- which is itself a pretty big question mark. If he continues to struggle, expect the Red Sox to try to unload him sooner rather than later; Beckett is owed more than $47 million through 2014, and the Sox' books are already bloated with aging, underperforming (or not-at-all performing) pitchers. The party might be over before he knows it.