Have you used FanGraphs' wonderful rookie leaderboard recently? If not, I recommend doing so, and lowering the plate appearance threshold all the way down to 0. Take a look at the American League position players. It sorts automatically by WAR - a counting stat - so there are precious few shenanigans afoot. Check it out. I'll wait.
Actually, I'm not going to wait. I'm too excited, sample sizes be damned. I'll do it for you. Take a look at line number 2:
How about that?
And, for those of you who may be curious, he ranks sixth among all rookie position players in WAR.