With Torii Hunter sidelined by a hamstring injury, J.D. Martinez has started seven of the last eight games for the Tigers and has certainly made the most of the opportunity, batting .400 (12 for 30) with three homers. He now has six homers in 100 at-bats, which for most players would obviously be too good to be true, but maybe not for one who has routinely trounced the minor leagues, batting .332 with a .942 OPS over six seasons.
In other words, you're right to be intrigued. At age 26, Martinez isn't beyond a breakout even if his previous stints in the majors all ended in disappointment. Just look at Lonnie Chisenhall.
Unfortunately, Martinez has even clearer threats to his playing time than Chisenhall. His latest home run Thursday was just his third hit of any kind off a left-handed pitcher, giving him a .094 (3 for 32) batting average against them. Rajai Davis, meanwhile, has always hit lefties well, batting .295 for his career and .302 this year.
Austin Jackson isn't sitting, so where does that leave Martinez when Hunter returns Sunday? In a platoon, most likely.
As mixed-league owners are finding out with Corey Dickerson, platoon players don't make for the most reliable starters in Fantasy. I'm not bothering with Martinez outside of AL-only leagues.