The Twins recently announced that Target Field would be a smoke-free facility starting in 2012. Apparently, they were not referencing tobacco products but rather Carl Pavano’s fastball.

Minnesota’s inning-eating stalwart of the past several seasons entered Opening Day in Baltimore and was not impressing any radar gun enthusiasts by tossing his fastball a touch over 85 miles an hour. On Saturday, Star Tribune columnist Jim Souhan reported that there were some organizational staffers were “alarmed” at this development.

[ATTACH=CONFIG]557[/ATTACH]

At Baseball Prospectus, former analyst and current Houston Astros’ staffer Mike Fast found that pitchers’ velocity is a bell curve over the course of the season:

“Fastball speed for an average major-league pitcher starts at its lowest point in early April, rises by about 1.0-1.5 mph to a peak in the month of July, and declines gradually thereafter. These trends apply similarly to starting pitchers and relief pitchers.”

As you can see from the chart above, like Fast’s research which showed velocity increased throughout the season, Pavano also had a gradual climb in velocity as the season progressed. In 2009 and 2010, he added roughly 2 miles an hour to his fastball. Last year, however, he was only able to dial up his heat 0.2 miles an hour. Meanwhile, this year, he has begun at his lowest starting point in the past four years. At 36 years old and coming off of two straight seasons of throwing over 222 innings -- not to mention a failure to ratchet up his fastball in 2011 like he did in 2009 and 2010 -- this may be an early indication that he could be wearing down indefinitely.

To be fair, Pavano, who has never been a hard thrower even in the early stages of his career, has always relied on his fastball’s command and movement over power. Because of its pedestrian nature in comparison to the rest of the league, when he misses his spots over the plate opponents have been able to lacerate his fastball (such as what happened when Nick Markakis launched a two-run home run off of him in the first inning of Friday’s contest). For instance, in 2009, the year in which the Twins traded for him at the waiver deadline, Pavano’s fastball was valued at -23.8 runs below average by Fangraphs.com – the worst rate in baseball among qualified starters. The following year it came in at -7.2, a fair improvement but still near the bottom of the league. Last season his fastball finished at -25.6, second only to A.J. Burnett’s -34. Despite all of that, Pavano has managed to remain a pitcher who has turned in consecutive seasons of 3 wins above replacement since 2009.

What allowed him to succeed despite the sheer obliteration of his heater was guile – throwing a decent combination of a slider and changeup that incited plenty of opponents to expand the strike zone and swing at less than favorable pitches. Between 2009 and 2011, he was able to get hitters to swing at 34.4 percent of out-of-zone pitches – the second-highest amount in baseball. In short, opponents were less likely to square up on a ball that is off the plate leading to more outs for Pavano in spite of chucking a lackluster fastball.

But here’s another factor that should be considered as his velocity declines: the differential between his fastball and his off-speed pitches is eroding. Along with his command and movement, the secondary pitches provided Pavano with a change of speed that disrupted the opposition’s timing. Baseball researcher Dave Allen discovered that the optimal differential between a fastball and a changeup to be effective is between 5% and 12%. In essence, anything below 5% and anything above 12% gives the hitter a better read on the pitch. For Pavano, in 2009 and 2010, he had an approximate nine mile per hour differential between his fastball and his changeup. This resulted in differentials of 10.2% in ‘09 and 9.4% in ’10. Last season, he posted a differential of 8.8%, still within the sweet spot Allen described but was definitely trending downward as his fastball’s velocity decreased. In just his one start, he held a differential of 4.5% slightly below the threshold for effectiveness. In theory, if Pavano continues to throw his fastball and changeup in this range, he will lose the ability to fool hitters with the off-speed stuff.

Yes, it is just one outing, and his first of the year at that, but there are some signs which suggest Pavano may be in line for a hard season if he is unable to add some MPHs to his fastball.