With a 2.38 ERA and .912 WHIP, Brandon Morrow seems to be off to a great start for the Toronto Blue Jays in 2012. However, his 4.33 FIP may indicate he's in line for some regression soon.
What's interesting about Morrow's season so far is that he's been recording the majority of his outs on sliders, while his fastball has been getting hit fairly hard. Through his first six starts, Morrow's fastball has a .397 wOBA against, and his .681 slugging percentage against is third worst in baseball. All seven of the home runs yielded by Morrow have come off the fastball, as well as eight of ten doubles.
Morrow's slider is hitting the strike zone 41.4% of the time. Batters are chasing his slider out of the zone 39.0% of the time; eventually, they'll lay off the pitch more and sit on the fastball, which could precipitate that regression.