Throughout his six-year MLB career, Brandon Morrow has tantalized us with his potential. He was capable of elite strikeout rates, but his spotty control and penchant for the long ball held him back. Last year Morrow turned in his best single-season pitching performance to date, and it’s a shame that he got hurt after just 21 starts and 124.2 innings. He was on pace for a 196-inning, 15-win season for the Blue Jays.Not surprisingly, improved control and an increased ground ball rate (leading to fewer homers) were the primary factors fueling his breakout, but like most pitchers who experience drops in walk and fly ball rates, Morrow’s strikeout rate fell as well. PitchFX data provided by BrooksBaseball.net indicates a change in approach in 2012 led to Morrow’s new outcomes.Morrow’s pitch selection, 2011 vs. 2012In 2011, Morrow threw his four-seam fastball 58% of the time, his slider 24%, his change-up 4% and any other pitch 14%. His average four-seamer clocked in at 94.6 mph. In 2012, Morrow threw his four-seam fastball 60% of the time, his slider 21%, his change-up 11% and any other pitch just 8% with his average four-seamer registering at 93.8 mph.That might not seem like much of a difference, but it leads me to two conclusions about Morrow’s 2012 season:He made a conscious attempt to specialize in three pitches versus varying upwards of six offeringsHe stopped rearing back for extra velocity, likely improving his control in the processA look at exactly when he threw each pitch bears out his transformation much more clearly.A look at the tan-shaded lines shows how Morrow approached both left-handed and right-handed batters in 2011 and 2012. Notice how in 2011 he threw change-ups just 6% of the time versus left-handed batters, but in 2012 he tripled that rate to 19% of the time. Against right-handed batters his approach remained very constant: fastballs and sliders. The notable change is the complete eradication of the sinker, which yielded a proportional rise in four-seamer usage.Explaining the decrease in walk and fly ball rates from 2011 to 2012One thing you might notice in the tables above is the rearrangement of the red and blue shading from 2011 to 2012, which corresponds to pitches Morrow threw 10% more or 10% less than his baseline usage, respectively. In 2012 you see the appearance of the blue shading in the four-seam category, indicating lower than normal usage, for when Morrow was ahead of left-handed batters and when he had two strikes on both righties and lefties.Against left-handed batters, Morrow traded in those four-seamers for change-ups. Prior to 2012, Morrow had always struggled with locating his change-up — he threw it for a ball at least 43% of the time in each of his first five seasons — but last year he missed the strike zone just 35.1% of the time with his change-up. Combined with his increased reliance on his change, that explains a great deal of his improved walk rate. The rest of it can be explained by the incremental annual rise of his fastball control. From 2008-2011, Morrow saw his fastball-for-a-ball rate drop three percentage points from 38.1% to 35.1% (lower is better) but last year alone it dropped over two percentage points to 32.9%.As for the increased ground ball rate, it also doesn’t hurt that Morrow’s career 2.61 grounder-to-fly ratio off his change-up is the highest of any of his several offerings, so more ground balls was a natural byproduct of his change in approach. Plus, from 2009-2012, Morrow increased the grounder-to-fly ratio of his slider annually from 1.40 in 2009 to 2.06 last year.Explaining the decrease in strikeout rate from 2011 to 2012Morrow’s strikeout struggles last year were due entirely to his difficulty striking out left-handed batters. While his strikeout rate (measured in terms of K%, or strikeouts per plate appearance) against right-handed batters remained stable from 2011 to 2012 (20.9% in 2011, 20.7% in 2012), his K% against left-handed pitchers dropped noticeably (28.6% to 23.5%). This decrease resulted in an overall drop in K% from 26.1%, the second-highest rate of his career, to 21.4%, the second-lowest.What could have caused this decrease? For whatever reason (velocity, movement, etc.) Morrow endured a drop in swings-and-misses generated by his four-seam fastball last year. In 2010 and 2011, Morrow’s two elite strikeout seasons, he generated whiffs on about 10% of his four-seamers. Last year that rate fell to just 5.9%This didn’t have much of an effect on his strikeout rate against right-handed batters. Morrow turned to his always-effective slider in two-strike counts against righties with greater frequency in 2012 than 2011 (48% versus 40%), which helped offset the drop in four-seamer whiff rate. In two-strike counts against left-handed batters, he used his slider as much in 2012 as 2011 (41% in 2012, 39% in 2011) but also featured his change-up with increased frequency. In terms of generating swings and misses, his change-up was less than half as effective as his slider (10.8% whiff rate for change-up, 23.2% for slider).To sum all of that up, overall from 2011 to 2012 Morrow saw his fastball velocity decrease. With it his strikeout effectiveness with the fastball plummeted. He was still able to maintain the same strikeout rate versus right-handed batters due to a noticeable rise in his slider usage, his premier swing-and-miss pitch, in two-strike counts to righties. He was unable to maintain the same strikeout rate against left-handed batters because the pitch he used 47% of the time in two-strike counts to righties (his four-seamer) was half as effective at generating swings and misses as it was the year before, and instead of increasing his slider usage to generate strikeouts he turned to his much less effective change-up (much less effective in terms of generating whiffs).Looking ahead to 2013If we could construct the perfect season for Morrow in 2013, it would look something like this:Fastball velocity and whiff rate return to or surpass 2010-2011 levelsIncreased change-up usage from 2012 persists, which would keep his ground ball rate upControl of his four-seamer and change-up remains improved from 2010-2011 levels, which would keep his walk rate downIt’s only been one start and 100 pitches, but it appears all of these things have happened.Morrow’s velocity has risen drastically. In his first start this year his fastball averaged a robust 95.4 mph. Recall that last year Morrow’s average fastball was just 93.8 mph, and in his first start of 2012 it averaged just 91.9 mph. While he induced swings and misses on just 5.9% of his four-seamers last year, he boasted a gaudy 15.7% whiff rate in his first start of 2013.Morrow’s increased change-up usage has carried over from last season. In his start against the Indians on April 3, he tossed his change-up 15 times (for a 15% usage rate) and featured it prominently to left-handed batters (17% of the time) just like he had the year before.Morrow’s control has remained improved. Of the 51 four-seamers he threw in his first start of 2013, only 33.3% of them were balls, which is right in line with his 32.9% rate from last season. While that sample size is still very small, the sample size of 15 change-ups is absolutely impossible to draw anything meaningful from, but for what it’s worth he missed the strike zone on 46.7% of those 15 change-ups. For now, just remember that he walked only two batters in those six innings, which isn’t too bad.With his fastball dominance restored and his increase change-up usage from 2012 carrying over to 2013, Morrow could be poised for a return to his elite strikeout rates while maintaining his improved control and ground ball rates. That could be a devastating combination for American League batters and makes Morrow a sleeper candidate to insert himself into the AL Cy Young discussion — if he can stay healthy.