Prospect of the Day: Robbie Ray, LHP, Detroit Tigers

Rookie left-handed pitcher Robbie Ray will make his major league debut this evening for the Detroit Tigers, taking on the Houston Astros. Acquired over the winter from the Washington Nationals for veteran right-hander Doug Fister, Ray was off to an excellent start in the minors this spring, making him a logical subject for Tuesday's Prospect of the Day.

Ray was drafted by the Nationals in the 12th round in 2010, from high school in Brentwood, Tennessee. Don't be deceived by his draft position: he was considered a second-round talent but fell due to signability concerns and a University of Arkansas commitment. It took an over-slot $799,000 bonus to sign the southpaw.

Ray emerged quickly with a strong showing in 2011, posting a 3.13 ERA with a 95/38 K/BB ratio in 89 innings for Low-A Hagerstown in the South Atlantic League. At this point his changeup was his best pitch and he didn't rank particularly highly on most prospect lists due to a mediocre fastball: he threw harder in high school than he did at Hagerstown, although the results were solid. .

He threw slightly harder in '12, boosting his fastball from 87-91 up to 90-93 on his best days. Despite this, he had a terrible season with a 4-12, 6.56 line for High-A Potomac, with 122 hits allowed in 106 innings and an 86/49 K/BB. He gave up 14 homers. He still had a decent changeup but scouting reports indicated that his breaking ball deteriorated and Carolina League hitters took advantage of that weakness.

2013 was much different: Ray opened with a 3.11 ERA in 15 starts at Potomac with a 100/41 K/BB in 84 innings, then remained effective with a 3.72 ERA and a 60/21 K/BB in 58 innings for Double-A Harrisburg. Overall he went 11-6, 3.36, 160/62 K/BB in 142 combined innings with 116 hits, a fine performance all around and massively improved compared to '12. He came to Detroit in the December 2013 Doug Fister trade and is off to an excellent start in '14, with a 1.53 ERA in 29 innings for Triple-A Toledo, with a 21/5 K/BB.

Ray is a 6-2, 195 pound lefty born October 1, 1991. Ray threw 92-95 MPH in high school, then dropped down into the 80s in '11. With maturity and mechanical refinements he has gradually regained his velocity, back into the low-90s and occasionally as high as 95-96. His changeup has always been solid, but the key over the last year has been an improved breaking ball. It's not terrific but it is better than it was two years ago when he was getting hammered in the Carolina League. He's shown excellent command of all three pitches this spring, another reason for his step forward.

If Ray continues to progress with his breaking ball and maintains the command he's shown for Toledo, he could be a fine mid-rotation starter. His delivery helps his pitches play up against left-handed hitters, making bullpen usage a backup option if he fails as a starter.

Keys to watch for this evening: does he challenge hitters or does he nibble too much? Does he keep his mechanics consistent? And how does that breaking ball look?