You all know the story by now.  In a span of 5 months, Jon Lester has transformed from a shaky 5th starter on the brink of a demotion to a legitimate ace.  His walk rate and HR rates have plummeted, and as a result he has allowed 30% fewer runs than a year ago.  He’s already had 2 CG shutouts this season (including a no-hitter), and he had yet another strong performance last night.

So, what has changed?  Clearly he is allowing more contact this year, as his K rate has dropped from 7.1 to 6.1, but his ground ball rate has increased even more (a 40% increase in ground balls compared to a 15% decline in strikeouts).  How does his stuff differ this year from last?

Let’s take a look at a Lester start from the beginning of the season. 2008 began much like 2007 ended for Lester: painfully.  In his first 6 starts, Jon allowed 19 walks (compared to 16 Ks) and 5 home runs.   Since those 6 starts, Lester is clearly a different pitcher.  I’ll use his fourth start of the season for this analysis (assuming he was naturally rusty or fatigued from the Japan trip in his first few starts).

On 4/14/08, a day before my 30th birthday, Jon Lester pitched 4.1 forgettable innings, walking 5 and striking out 3.  Here’s the breakdown of his pitches, courtesy of BrooksBaseball.net (if this website were a woman, I would make sweet love to it for 36 hours straight):

Now, let’s have a look at his memorable start on 5/16/08 (the no-hitter):

And finally, Jon Lester’s 7.1 inning start last night, where he held a tough Texas Rangers lineup to three runs on 7 hits (i.e. a more realistic example of a typical Lester start):

The biggest difference (aside from the monumental fact that he is throwing his fastball and cut fastball for strikes more often) is in his breaking pitch.  It’s faster and tighter, almost as if it is a slurve (a cross between a fastball and a slider).  He’s certainly been locating it much better than before, when it was more of a traditional vertical breaking curveball.

As Lester’s approach continues to improve, the Red Sox should have an impressive 1-2-3 rotation down the stretch.  It’s a combination that would be ideal for a short playoff series.