This is the fourth annual installment of my "guys I got wrong" piece. I'll look at players who've become much better big leaguers than I ever forecast them to be, and try to explain where I made mistakes in evaluating them.

Last year I began including some players I didn't discuss much as prospects or young major leaguers, errors of omission that are errors nonetheless. I've continued that this year to talk about some guys who never received much praise or publicity anywhere, not just from me.

Note: When discussing grades, I am referring to the 20-80 grading scale that scouts use.

I had Pollock rated just ninth in the Diamondbacks' system going into the 2012 season, which in hindsight seems particularly silly, as Pollock had had a solid 2011 campaign in Double-A, hitting .307/.357/.444 after missing all of 2010 due to injury. I thought Pollock could hit, but more in the .270-280 range without power or walks, and I didn't at all foresee him becoming an elite defensive center fielder; his UZR (Ultimate Zone Rating) is plus-16 per 150 games over an average defender in his major league career.

When Pollock was an amateur at Notre Dame, he used the middle of the field and almost flung the bat at the ball, getting no lift in his swing. He was also a 55 (above-average) runner in-game, which made him more of an average or slightly better defender in center. The Diamondbacks saw more raw power from him in their pre-draft workout, and he ran faster in that workout than he had in college, all factors in their decision to take him 17th overall in 2009. Their player development staff has done a lot of work on his defense and getting him to pull the ball for power, and after several years of changing his leg kick, he went back this year to what used to work for him when he was younger. Add to that his outstanding work ethic and you get a player who has produced 7.2 WAR (per Baseball-Reference) this year.