From 2009-2011 Weaver's been a top 15 pitcher, accumulating 14.8 fWAR in that time. He's struck out over 22% of batters he's faced, while walking just 6.5%.
That comes out to a 15.8 K-BB%, which is pretty solid. In 2012 the league average K-BB% for starters was 11.4%, so that can give you a little idea of how Weaver ranked.
For more on K-BB%, check out Glenn's piece from Sunday.
In 2012, though, Weaver struggled. He suffered through a back injury, which could have been a contributing factor, but he saw his strikeout percentage drop to 19.2%. His BB% remained fairly static, finishing the season at 6.1%. His K-BB% (13.1%) was still above average.
Immediately, one big cause for concern that I noticed was the decrease in the velocity of his fastball. Weaver doesn't have a ton to work with in terms of fastball velocity. Career-wise he sits around 90 miles per hour.
From 2007-2011, Weaver's fastball hovered between 89-90 miles per hour. His sinker, which was his most popular pitch next to his fastball, sat between 91 and 89 miles per hour.
In 2012 he saw both pitches lose velocity though. His fastball lost almost 2 miles per hour, and his sinker lost nearly 2 miles per hour as well.
While his sinker did lose velocity, it appears that he didn't entirely lose its effectiveness. He never generated a ton of whiffs on swings with the pitch, his career whiff/swing% with his sinker is a little over 13%, and in 2012 it was right around 12%.
He managed to give up less line drives with the pitch than a year ago. In 2011 his sinker had an 18% LD%, compared to a 12% LD% in 2012. He also saw his groundball percentage rise with his sinker, going from 28% to 38%.
Weaver's fastball did suffer though.
Career-wise Weaver has a 17% whiff/swing percentage when throwing his fastball. Yet in 2012 he saw it fall to 12%, which was a career low.
I was interested to see if Weaver had any change in his pitch selection from a year ago, so I headed over to Brooks Baseball, and got the necessary data.
In 2012 Weaver used his fastball and sinker more often than not, as I stated earlier. If he had a batter in an 0-2 count it was almost certain that the batter was going to see a fastball. When he got behind the batter 2-0 he would use his change-up 29% of the time. If he was ahead in the count 1-2 or 2-2 he'd also get his slider in there as a potential strikeout pitch.
Now let's look at 2011 to see if anything changed.
Weaver threw his slider more in 2011, particularly in 0-2 and 1-2 counts. In 0-2 counts he threw it 28% of the time, and in 1-2 counts he threw it 34% of the time.
He also threw his change-up more in 2-2 counts. He did throw his sinker less in 2011 as well.
Even though he was throwing his slider more in 2011, he actually had more success with it during the 2012 season. In 2011 he generated groundballs 29% of the time when he threw his slider, compared to 43% in 2012.
So while his pitch selection changed, it's hard to get a lot of conclusive evidence out of this information.
Weaver has seen his O-Swing% decrease since 2010, based on this data it is not unreasonable to suggest that he peaked in 2010. Still he did see his O-Swing% decrease by over 1% since 2011. Everything else sat around league average for the most part, although his Z-Swing% was below average by roughly 3%.
His F-Strike% was above average, but his SwStrk% was below average, albeit slightly. Not too much can be taken out of this in terms of a potential decline. Weaver will obviously want to get more first pitch strikes, but other then that, that's about it.
Weaver has always been one to have an ERA much lower than his FIP, and in 2012 that was no different. This past season he had an E-F difference of -.93.
That was the biggest difference since rookie year in 2006, when there was a -1.34 difference in his ERA and FIP.
His .241 BABIP was also abnormally low. It was .250 in 2011, and .237 during his rookie year, but with a .276 career BABIP he should see some changes in his ERA.
What is most concerning though has to be the loss of velocity on Weaver's fastball.
Weaver is 30 years old, and according to Bill Petti's research, thirty year old's only have .22 times the odds of regaining velocity.
They do have C.J. Wilson still, but he wasn't exactly great in 2012. It will be interesting to see what happens.