What He's Done to Get Picked Up in Fantasy:
Go on a pretty epic hot streak. Basically, hit the cover off the ball and be on an impressive power binge (five homers in his last eight games) and an OPS over .900 in eight of his last 10 games which has helped push his batting average up to .314.
I still remember watching the game where he made his MLB debut. He was with the Astros at the time and they were playing the Brewers. He came up to the plate and neither the people operating the scoreboard at Miller Park nor the announcers could figure out his name and I was thinking to myself "easy out". Martinez got the last laugh for that time being as he ended up hitting a double in that plate appearance but the Brewers still prevailed that day despite hitting Felipe Lopez fifth and letting Yuniesky Betancourt play defense.
What To Expect Going Forward:
He may stay on this hot streak for a little bit more time but regression is going to find him, a matter of if, not when. He is being fueled by a .367 BABIP (career total is .314). I'm thinking that the batting average is closer to the .270 range by the time this season is over.
One thing to see is whether he is actually improved his approach at the plate (besides being very fortunate over the last couple weeks). This appears to be a definite no as his BB/K ratio is actually worse this year than it is for his career. Another related red flag/risk to keep an eye out on is that he has gotten less selective which could make any future cold streaks very brutal as he has increased the percentage of pitches he has swung at outside the strike zone this year.
The one possible upside is maybe he improves his power totals going forward as he has hit less ground balls this year (38%) versus his career total (45%).
Still his HR/FB ratio is almost two times his career total and he's not going to hit homers on a regular basis forever. Assuming he continues to get decent playing time I could see him ending up in the 20-25 homer range (especially with the nice head start he has gotten). Either way, the Tigers have gotten very good value out of someone they signed to the league minimum while everyone was sleeping off their new years hangovers. Regression or not, they did well for themselves on a signing that was likely an after thought to the average fan.
With Brett Lawrie getting injured, (I moved him into the Disabled List slot instead of dropping him), I had an extra roster spot for offense and used that to pick up Martinez. While my expectations are modest he seems to be a decent source of power even if the batting average is a mirage and his stolen bases are non-existent.
While his most similar player (per his Baseball-Reference page), Chet Ross did not have a very long career (he played his last game at age 27) there are a few players on this list (George Foster, Ben Oglivie & Gorman Thomas) that went on to have fairly productive careers.
So far, Martinez has played a surprising contributing role on a Tigers team that while they are in first place (as expected), they have been nowhere near as dominant as everyone thought they would be this year. Martinez is not going to be an MVP but he appears on line to come out of 2014 with better than expected stats.
All numbers, stats mentioned found on either fangraphs.com or baseball-reference.com