A sleeper who woke up: J.D. Martinez, OF, Detroit Tigers

Detroit Tigers outfielder J.D. Martinez was one of the best hitters in the American League in 2014: among players with 400 or more plate appearances, Martinez ranked sixth with a 153 wRC+. His .315/.355/.553 line combined with Victor Martinez and Miguel Cabrera to give the Tigers lineup three of the top eight most productive bats in the junior circuit.

Cabrera and Victor Martinez have been excellent players for years, of course, but J.D. Martinez was little-known to anyone but Tigers boosters and Houston Astros fans six months ago. So, where did this guy come from?

Martinez was drafted by the Astros in the 20th round in 2009, from Nova Southeastern University in Florida. He'd hit a stunning .428/.530/.777 with 15 homers, 41 walks, and just 26 strikeouts in 187 at-bats that spring, but scouts had mixed opinions. His physical tools were pretty decent but many felt that his swing mechanics would not work at higher levels, thus hampering his draft stock despite the gaudy stats.

He got off to an outstanding start in pro ball, hitting .348/.399/.598 with 12 homers, 20 walks, and 44 strikeouts in 264 at-bats split between Greenville in the Appalachian League and Tri-City in the New York-Penn League. I wrote him up thus for the 2010 book:

The Astros drafted Martinez in the 20th round last year, out of Nova Southeastern University in Florida. He was a monster in college, and he was a monster in pro ball, too, dominating the Appalachian and New York-Penn Leagues in his pro debut, posting a +39 percent OPS at the latter stop and winning the league batting title. Martinez didn’t get a lot of pre-draft buzz, but his physical tools are rated as at least average by some scouts. Obviously pro ball wasn’t much of a challenge for him, and he looks to have legitimate hitting skills. Although we need to see how he responds to higher levels (his plate discipline needs some work), I think the Astros have a potential sleeper here. Grade C but should be tracked closely.

Martinez kept hitting in 2010, batting .362/.443/.598 with 15 homers, 33 walks, and 55 strikeouts in 348 at-bats for Lexington in the South Atlantic League, then .302/.357/.407 in 189 at-bats for Double-A Corpus Christi. The power dropped off in the Texas League, but he was skipping a level and overall he held his own. Here's the report I wrote entering 2011:

Martinez proved last year that his talents were real, destroying the South Atlantic League (+49 OPS) and holding his own after moving up to the Texas League (+7) without an intervening stop in High-A. The scouting reports are positive: he has a good swing and can drive the ball, and his physical tools are solid. About the only physical negative is mediocre running speed, but he is a decent athlete overall. No one seems to have a good explanation about how he lasted to the 20th round. I know he went to a smaller college, but still, a lot of people underrated this guy. I think he’s legit. Grade B-.

That report vaguely described his swing as "good" but it was still considered unorthodox because he strode with his front foot early. By "good" I meant that it still worked against better pitching and there were fewer complaints about it from observers.

Martinez wasn't in any more prospect books: he saw substantial playing time for the Astros in 2011, 2012, and 2013. He hit well at times but as hampered by injuries; his 2013 season was particularly difficult (just .250/.272/.378). Although the injuries didn't help, pitchers figured out the flaws in his swing. The Astros felt they didn't have room for him and he was removed from the roster last November.

The Tigers picked him up and it turned out to be one of the great bargains of 2014, as Martinez returned to the form he showed in the minors. Better health helped of course, but there was more going on here than simple injury avoidance.

Last December, Dan Farnsworth at Fangraphs noticed that Martinez had made some significant alterations to his swing during the Venezuelan Winter League last fall. After breaking down the swing changes including a different leg shift and a more direct path to the ball, Farnsworth concluded:

Baseball is no doubt a game of constant adjustments, and J.D.’s success in the LVBP this year shows that he is smart and athletic enough to improve himself into being a better hitter.  Just his minor league pedigree alone might have warranted interest from a team looking for a decent bench player with some modest upside.  However, the work he has done with his swing may be what pushes him back on track to being a respectable middle of the order threat for a competitive team.  The power is not in question, and if his hit tool is really starting to blossom he becomes an exciting player very quickly.

And that's exactly what happened.

Jeff Sullivan at Fangraphs points out that there has been a radical change in Martinez's spray chart profile this year. During his days with the Astros, almost all of Martinez's power came when he pulled the ball. Martinez hit 24 homers during his Houston days, and 19 of those were pulled to left. It is much different with the Tigers: he showed power to all fields this year. 13 of the 23 homers he hit for the Tigers this year were knocked to center field or right field.

After well-deserved praise to Farnsworth for his prescience, Sullivan concludes:

Fact: J.D. Martinez has succeeded this year in a big way, after changing the way that he hits.

Sub-fact: Martinez has succeeded by hitting the ball hard to all fields, which is an uncommon skill and a hard thing to fluke.

Theory: Martinez’s ability to spray line drives and dingers could mean he’s less likely to regress super hard.

I have to agree with that.

It would be one thing if Martinez was just doing this out of the blue, but he's not. He was a devastating hitter in college, and he was excellent in the minor leagues as well. However, he jumped directly to the majors from Double-A in 2011 and saw just 23 games in Triple-A in '12. The jump in competition, combined with injuries, forced him into a difficult adjustment period once major league pitchers got a good look at him.

Many young hitters don't make the necessary counter-adjustments, but Martinez did. Kudos to the player for making the needed change, kudos to the Tigers for recognizing his talent, and kudos to Dan Farnsworth for predicting that this could happen 10 months ago.