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Ryan Dempster: Pitch selection and success

The Astros were able to notch a victory for the first time this season, in large part by scoring against Cubs starter Ryan Dempster in his last two innings of work. On the whole, Dempster pitched fairly well: 6 IP, 6 H, 2 ER, 5 K, 3 BB. After being a relief pitcher from 2004-2007, Dempster returned to a starter's role in 2008, and did so seamlessly.

What could he have done to go from slightly above mediocre reliever to ace starter on the the NL Central Champions? One pretty important area where he altered his approach was in his pitch selection.

Looking at his 2007 and 2008 seasons, Dempster seemed to almost pitch backwards. Meaning that he threw his fastball much more frequently as a starter than as a reliever:

Season Fastball Slider Changeup
2007 46.1% 33.3% 20.7%
2008 55.% 27.4% 16.7%


A lot of what he did as a pitcher did not change much: his percentage of groundballs/flyballs induced, swing percentages and contact rates remained fairly constant. What changed a great deal for a one season flucutation were his strikeout and walk rates. He struck out nearly half a batter more per nine innings (7.43 in 2007 vs. 8.14 in 2008), and walked roughly three quarters of a batter less per nine innings (4.05 in 2007 vs. 3.31 in 2008).

Does throwing his fastball more mean he was more aggressive as a starter than a reliever? Batters were slightly more apt to swing at balls in the strike zone in 2008, than in 2007. Again, this all seems backwards. Relievers are known as strike zone pounders, never ones to want to pitch tenatively. They're firemen, summoned from the bullpen to put out offensive flames. Walking batters is some of the best fuel to keep a blaze going. Perhaps when he became a starter, Dempster learned this lesson or at least took it more to heart.

The sample size is not significant, but let's take a look at what Dempster did last night, in terms of pitch selection:

Pitch Number Thrown % Thrown of Total
Four Seam Fastball 43 47.77
Changeup 12 13.33
Slider 30 33.33
Curveball 3 3.33
Two Seam Fastball 2 2.22


It's just one start, but his pitch selection had more in common with his style in 2007 than in 2008. He struggled the most in the fifth and sixth innings, where his strike percentage was below 60% in both. While it remains to be seen how Ryan Dempster will approach his 2009, it does appear that he is most effective when he throws his fastball with greater frequency.