Morrow was drafted by the Seattle Mariners in the first round in 2006, fifth overall, from the University of California. His college track record was mixed: he pitched poorly as a freshman (6.07 ERA in 30 innings, 18/19 K/BB) and was even worse as a sophomore (9.36 ERA, 25/20 K/BB in 25 innings). However, he looked much better against wooden bats in the 2005 Cape Cod League, posting a 1.84 ERA with a 24/9 K/BB in 15 innings for Yarmouth, being used as a closer. He took a big step forward as a starter in the spring of '06, posting a 2.05 ERA with a 97/39 K/BB in 97 innings for the Golden Bears, hitting 99 MPH and showing a good slider and splitter.
There were two main questions for Morrow: would he throw enough strikes, and would he start or relieve in the majors? He's diabetic but has the condition under control, so that wasn't an issue. He got 16 innings of pro ball between the Arizona Rookie League and the California League, giving up four runs with a 17/9 K/BB. I gave him a Grade B+ in the '07 book, and wrote that "I really like his ceiling, but he may need a little more development time than some college aces."
Morrow was so impressive in 2007 spring training that he made the major league roster, being used in relief. He posted a solid 4.12 ERA (ERA+107) but with a poor 66/50 K/BB in 63 innings: the strikeout rate was good, but there were too many walks. He improved in 2008 with a 3.34 ERA (127 ERA+), 75/34 K/BB in 65 innings, picking up 10 saves but also starting five games. However, his control slipped a bit in '09 (63/44 K/BB in 70 innings, ERA 4.39, ERA+98), and he was traded in December to Toronto for pitcher Brandon League and outfield prospect Johermyn Chavez.
As you know, Morrow went 10-7, 4.49 ERA, 3.16 FIP, 3.48 xFIP with a 178/66 K/BB in 146 innings last year, giving him a WAR of 3.7. He's off to a strong start so far in '11, which makes sense given that his FIP and xFIP were much better than his ERA last year. Overall, in his major league career, Morrow has a 4.13 ERA with a 405/201 K/BB in 362 innings, 312 hits allowed, an ERA+ of 102, FIP 4.13, xFIP 3.18, WAR 5.4.
Morrow got close to 100 MPH in the pen and pitches in the low-to-mid-90s as a starter, averaging 93.9 MPH with the Jays. He makes extensive use of his slider and curveball, but hasn't used a changeup much in his first starts of 2011 according to Pitch F/X. The metrics indicate that the slider has been his most effective pitch over the last three years. He missed the first part of this season with elbow soreness, but hasn't shown ill effects since returning.
Morrow's K/IP ratios are excellent, and I think he has the stuff to be a number one or two starter if the command and health are there. He's capable of being one of the best pitchers in the league. My thinking is that his command will gradually improve and that he is going to have some outstanding seasons, but that he will have more health issues to work through and might not be a Verlander-type 200+-inning-per-year workhorse.