A.J. Pollock seems a bit like a Rorschach test: Teams see what they want to see in him. Some see a center fielder. Some see a No. 2 hitter. Some see a middle-of-the-order slugger.
The challenge in evaluating Pollock is that at some point in his career, he's been pretty much everything you'd want a player to be. In his breakout 2015 season, Pollock played 157 games, hit for average and power, stole 39 bases, controlled the strike zone and was an outstanding defensive center fielder.
Since then, he's played 237 games -- under 50 percent -- while seeing his walk rate decline, his strikeout rate increase, and his overall offensive production drop well off. When teams look at Pollock as a possible free-agent addition this winter, then, they must decide whether they are adding an answer or a question.
That makes him one of the more puzzling potential middle-ticket free agents in this class. Bryce Harper, at the top of the outfield market, obviously comes with health and production questions as well. But he's 26 and has significantly outproduced Pollock for four years running. Nelson Cruz has decline risk, but is a known quantity.
The just-signed Michael Brantley, who has frequently been mentioned as a parallel for Pollock, is coming off a better and healthier year at the plate, though he's not the same defender. So the challenge is figuring where on that continuum Pollock fits -- and deciding whether the better bet might be to move up the ladder to Harper, or down to a bounceback candidate on a one-year deal.
If you're representing Pollock, you're selling that 2015 season, and saying if he stays healthy, a team is adding an MVP candidate type of player with a broad base of skills. If you're looking at paying him, you're asking a lot of questions about those concerning trends in health and production.

Let's be clear: It's not that Pollock can't play. He's been worth 5.5 bWAR over the past two seasons, even with a league-average bat. It's just that framing him as a difference-maker seems optimistic -- because ever since his return from injury, he's been a league-average hitter (102 OPS+ since the start of 2016). The speed remains attractive and gives some hope that he can remain a plus outfielder -- but at 31, with an injury history, that's no guarantee
The power is still there, but if his contact and strike-zone control continue trending the wrong direction, he starts looking like a very familiar offensive profile: right-handed, low-OBP slugger. Those guys' value is trending down, not up.
As fantasy analyst Ron Shandler is fond of saying, "Once you display a skill, you own it." In that light, it's again worth remembering that Pollock has displayed virtually every skill an outfielder can have. If he can stay healthy, and display it all again, you get a star.
So which is it?