It is no secret that the Rockies season will be determined in large part by the starting rotation, specifically Jorge De La Rosa. In 2009, De La Rosa won 16 games and was a catalyst in the Rockies playoff push that year. From June 5, 2009 to April 25,2010, De La Rosa went 19-4. The Rockies need a capable and healthy De La Rosa to have any shot at contention this year. But will he be the same pitcher?
In 2009, De La Rosa posted a 9.39 K/9 rate. Generally speaking, a pitcher that strikes out a batter an inning is labeled a "strikeout" pitcher, and DLR was just that with a K% of 24.2 in 2009. His average fastball that year was 93.4 mph. However, since coming back from Tommy John surgery [SMALL SAMPLE SIZE ALERT], De La Rosa's K/9 innings in 10 2/3 innings of work was 5.06, a significant drop. He also saw his K% drop to 11.3. In addition, his average fastball velocity dipped to 90.4.
De La Rosa's success comes from his ability to generate strikeouts. His ability to generate strikeouts came from his above average fastball complimented by his slider and changeup. The difference in velocity between his fastball and changeup in 2009 was about 10 mph, and the difference from his fastball to slider was also about 10 mph.
In 2012, the difference from his fastball to his slider was only about 6 mph. His fastball to changeup difference remained at about 10 mph. The chart below demonstrates how De La Rosa's K/9 innings has dropped the last several years as the velocity between his slider and fastball has gotten closer and closer together.
There is a precipitous drop from 2011 to 2012 in his K/9 from just below 8 K/9 to just above 5 K/9. As the chart shows, as his difference in velocity between FB and SL declines so do his strike outs. Typically, the better a pitcher can change speeds, the more strikeouts he can generate. If De La Rosa's fastball doesn't return, and he becomes a pedestrian strikeout pitcher, can he still be an effective pitcher? It's hard to say definitively, but it's doubtful that he can return to his old form without similar strikeout numbers. Strikeouts are certainly not the only way a pitcher can be successful and by no means is velocity difference the only way to tell if a pitcher has lost his stuff or not.
They can help to paint the picture though.
De La Rosa's recovery should also be taken into consideration. There are many pitchers that have undergone Tommy John surgery since its inception, and there are many success stories. Unfortunately, there are also examples of pitchers who never seemed to fully recover.
In most cases, recovery from Tommy John surgery takes about two years. However, given medical progress as well as the type of treatment afforded a big leaguer, that process can be shortened. Chris Carpenter underwent Tommy John surgery in July 2007 and his next full season in 2009 was arguably his best ever. Stephen Strasburg underwent Tommy John surgery and was excellent in his first year back; however he was shut down after reaching 160 innings pitched. Adam Wainwright's first full season after Tommy John had mixed results; he struggled early in the season, but progressed as the season went along.
Kerry Wood and former Rockies hurler Mike Hampton are two examples of pitchers that couldn't make it back - or in Wood's case, made it back only to suffer setback after setback. The fact that De La Rosa had two setbacks during his rehab is a tad disconcerting.
It is almost impossible to predict what the Rockies will get out of De La Rosa this season. The true test will be when the season starts and De La Rosa is dealing to big league hitters in a regular season game. Spring Training can only offer so much evidence as to whether or not he is ready for the rigors of a full MLB season. Only time will tell if he can be a factor this year for the Rockies.
Realistically, it could take De La Rosa close to a full season to fully bounce back from the surgery. If that is the case, will the Rockies risk exercising the option on his contract for $11 million next year?
Here's a list of Tommy John surgery patients
And a link to some successful and not so successful comebacks from Tommy John surgery