Missing: Tommy Hanson's Fastball

The Los Angeles Angels acquired Tommy Hanson from the Atlanta Braves on Friday in exchange for Jordan Walden, adding a 26-year-old starter who once looked like a burgeoning ace but now has serious questions to answer about his health and his no-longer-fast fastball.

Hanson was a stud during his first full season in the majors in 2010, topping 200 innings and posting an ERA that was 17 percent better than the league average (117 ERA+). But he hit the DL twice in 2011 with a right shoulder injury, tossing 130 innings with an ERA just a smidge better than average (106 ERA+). This past season, Hanson again battled shoulder problems while throwing 174.2 frames and compiling an ERA that was 11 percent worse than the NL average. Hanson had the ninth-worst ERA+ among qualified NL starters, besting just Tim Lincecum, Joe Blanton, Barry Zito, Bud Norris, Edinson Volquez, James McDonald , Kevin Correia and Ricky Nolasco.

Hanson has to hope he re-discovers his fastball on the West Coast. His ERA has soared as his velocity has dipped: Hanson's fastball averaged 92.7 MPH during his stellar 2010 season, but he sat at 91.1 MPH in 2011 and fell to just 89.6 MPH in 2012. No longer able to bring the heat, Hanson has contracted a serious case of gopheritis.

Back in 2010, batters slugged .405 against Hanson's fastball (below the .430 average for NL starters) and hit 13 home runs. In 2011, Hanson's fastball slugging percentage jumped to .519, and he served up 11 homers despite throwing over 70 fewer innings than the previous season. This past year, Hanson arguably had the worst fastball among all regular NL starting pitchers. He had the highest fastball slugging percentage this side of J.A. Happ, who moved to Toronto to take advantage of the Canadian homer exchange rate:

Highest opponent slugging percentage on fastballs among NL starters in 2012, minimum 500 thrown

Pitcher	Slugging Pct.
J. A. Happ	.595
Tommy Hanson	.538
Christian Friedrich	.531
Bud Norris	.522
Ricky Nolasco	.518
Shaun Marcum	.514
Randy Wolf	.509
Chris Young	.505
Patrick Corbin	.504
Joe Blanton	.503
NL Avg. for SP	.435

And only Yovani Gallardo gave up more homers with his fastball:

Most HR allowed on fastballs among NL starting pitchers in 2012

Pitcher	HR
Yovani Gallardo	20
Tommy Hanson	18
Clayton Richard	18
Homer Bailey	18
Edwin Jackson	17
Ian Kennedy	17
J. A. Happ	16
Bud Norris	15
James McDonald	15
Chris Young	13

If Hanson's shoulder is sturdy and his fastball velocity returns, the Angels probably won't regret trading a high-octane (if erratic) arm like Walden for a reasonably-priced starter who is under team control through the 2015 season. If Hanson's heat doesn't come back, though, they might have just acquired a red-headed Ervin Santana.