Something is wrong with Tim Lincecum. After giving up five runs in his first start this year, things got worse for him last night. In just 2.1 innings, Lincecum allowed six runs on nine hits while walking two and striking out only one batter. While it’s usually not smart to make conclusions based on just 7.2 innings, Lincecum has already shown some reasons for folks to be concerned. And unless something changes, Lincecum could be in for a rough season.

After his first start, some writers wondered about Lincecum’s velocity. A look at the Pitch f/x data confirms those questions. Last season, Lincecum averaged 92.2 mph on his fastball. In his first start of the season, his fastball averaged 90.0 mph. And while critics will be quick to point out that it was just one start, as Jeff Zimmerman pointed out last June, pitcher velocity stabilizes after just one start. There’s a chance Lincecum could increase his velocity as the season goes on, but according to Jeff’s article, it will only increase by a maximum of 0.8 mph. The early returns on Lincecum’s second start aren’t encouraging, either. Lincecum’s velocity was even worse last night, according to Brooks Baseball.

Velocity loss has been a growing concern for Lincecum, and the speed on his pitches has been in steady decline since his rookie season. After compiling 15.5 WAR between 2008 and 2009, Lincecum dropped to 9.3 the past two seasons. While 9.3 WAR is still good enough to make him the 12th-best pitcher during that time, he rated as baseball’s top pitcher in 2008 and 2009.

With his diminished velocity, Lincecum has also seen his peripherals drop. In his first full season, Lincecum struck out 28.6% of the batters he faced. That number dropped to 24.4% last year. That’s still pretty exceptional, but the number is declining. What’s more concerning is Lincecum’s walk rate. Lincecum’s BB% fell to a career low 7.5% in 2009, but it jumped to 9.6% last year. And even though he has lost velocity in the past and succeeded, you have to wonder how long he can be effective if his fastball averages 90 mph the whole season.

Lincecum combated his decreased velocity by developing one of the nastiest changeups in baseball. In the past, Lincecum’s change has been about 9 mph behind his fastball. This season, the difference between the two is about 7 mph. That small change can produce some pretty awful results: Essentially, the smaller the mph difference, the less effective a change-up becomes. That could be the case this season as Lincecum’s changeup currently has a negative pitch-type rating, the first time that’s happened in his career. Sure, were only talking about two games, but if Lincecum can’t increase his velocity, it’ll be interesting to see whether he can still effectively use his changeup.

Lincecum already made headlines this season when he said that he planned to scrap his slider. While he’s made the decision so that he could stay healthy, he may want to reconsider if his struggles continue. Lincecum’s slider has always rated well, according to pitch values, and it would give him another effective pitch. It couldn’t hurt for him to at least experiment with the pitch if he can’t return to form over the next few starts.

While Lincecum has seen some signs of decline in the past couple years, this latest velocity change could be a sign that something is seriously wrong. Unless he regains his lost velocity, or he alters his repertoire, his run as an elite pitcher might be in jeopardy.