Despite his 5.48 ERA, Ryan Dempster continues to prove that his terrible April (9.58 ERA) was just an aberration, and that he should still be considered one of the better pitchers in the NL Central.
Dempster's xFIP of 3.31 is the best of his career, and his peripheral numbers are similar to his 2008 to 2010 numbers (3.11 BB/9 and 8.48 K/9).
Dempster ran into trouble in April because he allowed a staggering nine home runs in 31.1 innings pitched, a 23.7 percent HR/FB ratio. The home run ratio, along with a high BABIP of .320 and a below-average strand rate of 66.8 percent, have inflated his 2011 ERA.
His batted-ball rates are very consistent with his career numbers, so his ERA will decrease as his BABIP improves closer to his career .302 average.
Although Dempster is pitching the same way as he did last season, there are some signs that he is either not 100 percent healthy or that he has lost some arm strength. His average fastball velocity is down slightly from last season, dropping from 91 mph to 90.2 mph and it is ranked as the least effective pitch, according to pitch value on fangraphs.
His overall swinging-strike percentage (8.5 percent) has dropped from last season (10.9 percent), and his contact rate has increased from 75 to 81.5 percent. His fastball swinging-strike percentage is exactly the same as last season (11.1 percent), but his slider's swing-and-miss rate has dropped significantly from 38.9 to 26.3 percent.
Notwithstanding, Dempster showed increased velocity over his last few starts and the dip in velocity could be the product of the cold weather in April and the early part of May.
It is worth keeping an eye on, but Dempster can still succeed if his strikeout rate dips because of his ability to generate ground balls.