The red dots represent Johan Santana's maximum four-seam fastball velocity in each of his 2009 starts. The blue dots represent average four-seam fastball velocity. All data is from Brooks Baseball, which is missing Santana's Opening Day start for some reason. The rest of his starts are available:
(click to embiggen)
Reduced strikeout rate and decreased velocity are often signs of injury. Santana has struck out just 8 in his last 3 starts, spanning 16 innings. His average fastball velocity has hovered around 90 mph in these starts, after being in the 91-91.5 range early on. The man says he's not hurt (although Dan Warthen says he has some minor aches and pains), so it's possible this is just a "dead arm" period. Either way, Saturday's start vs. the Rays is a pivotal one. I'll be more interested in his radar gun readings than the outcome of the game.
Check out Tommy Rancel's post at Beyond the Boxscore for more on Santana. Tommy correctly notes that in recent years Santana's velocity has experienced peaks and valleys.