When Roy Halladay was added to the Phillies pitching staff in December 2009, much talk was made about how Halladay would serve as a mentor for Cole Hamels and how Halladay would help him learn how to pitch. The talk of how Halladay’s presence would make Hamels better continued through spring training and into the 2010 season as Hamels started to throw the cut fastball. There was also talk about how Hamels could help improve Halladay’s changeup. After a season and a half together, it seems as good a time as any to see if there are noticeable difference in their pitching style and results.

In 2010 Cole Hamels reduced his reliance on his fastball and changeup after learning to throw a cutter. In 2011 the cutter has become his 2nd most frequent pitch. The ability of Cole Hamels to add a 4th pitch has lead to a significant improvement in GB/FB ration, K% and xFIP. In 2010 Cole Hamels set a career low for xFIP and in 2011 he is on pace shatter that mark.

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Doc Halladay spent his career in the American League as a three pitch starter. He had a fastball, cutter and curveball that were over 95% of his pitches. His changeup was a rarely used pitch that did not compare with the rest of his arsenal. Since joining the National League, Halladay’s changeup was written about by Dave Allen of fangraphs in August 2010. Since joining the Phillies it has improved from a below average pitch (wCH-1.2) to a plus pitch. In 2011 Halladay has used his changeup more than his curveball. By increasing his repertoire, Halladay turned in one of the best seasons of his career in 2010 and has continued to improve in 2011 as his xFIP would be a career low.