The Breakthrough of Diamondbacks outfielder A.J. Pollock

One of the best players in baseball right now is outfielder A.J. Pollock of the Arizona Diamondbacks. The slash numbers are strong: .317/.371/.494. In relative context this is very good, the wRC+ coming out at 131, which ranks ninth in the National League. His glove is excellent, ranked third among National League outfielders by fDEF. He's stolen 33 bases in 40 attempts. Put the offense and defense together and his 5.5 fWAR ranks fourth in the NL; the only outfielder who ranks higher is Bryce Harper.

Basically Pollock does everything well: hit for average, hit for power, get on base, swipe bags, and field his position cleanly. It is notable that his 2014 season was virtually identical rate-wise albeit in a smaller sample: .302//353/.498, wRC+135, fWAR 3.3 in 75 games. He's performed like a star the last season and a half, outplaying many players with more press.

Some people are surprised by Pollock's outburst but perhaps we should not be. He was a multi-skilled star at Notre Dame, hitting .365/.445/.610 with 10 homers and 21 steals his junior year in 2009, which got him drafted in the first round, 17th overall. At the time many experts considered this a slight overdraft: Pollock's physical tools were considered solid across-the-board but not genuinely outstanding: he was generally regarded as a safe but unexciting draft pick.

Pollock missed all of 2010 with an elbow injury. He came back in 2011 with a .307/.357/.444 mark in Double-A, with 41 doubles, eight homers, and 36 steals. Note the broad base of contributions. In my 2012 book I wrote that Pollock "isn't likely to become a big home run hitter, but he'll hit for average, get on base, knock some doubles, and annoy pitchers with his aggressive and effective baserunning."

That projection remained intact with a .318/.369/.411 run through Triple-A in 2012 with 21 steals, still showing the broad base of skills. The lack of home run power (just three homers that year) was the main flaw and many observers (including this one) projected him as a really good fourth outfielder but not a star.

Pollock was a league-average National League hitter in 2013 with a .269/.322/.409 mark but his defense kept him in the lineup every day and elevated his fWAR to 3.3, making him a solid regular and not just a reserve. As noted above, the power surge developed in '14 and has stayed with us this year, combining with his other skills to make him one of the best regular outfielders in the game.

Was it predictable? If you look back at the old scouting reports, the optimists felt Pollock could develop 10-15 home run per season power. He's at the upper edge of that expectation these days, with overall production boosted because he's proven to be a .300+ hitter rather than the .260-.280 type predicted by his original traditional scouting reports as well as his sabermetric projection numbers for Mobile and Reno.

Comparing current observations to old notes from the 2009 Midwest League and the 2012 Pacific Coast League, I don't see any massively obvious changes in his hitting approach. He's always scouted as a guy who could hit the ball with some authority to all fields, showing more power to the pull side but not excessively or as strictly a pull hitter, while making consistent hard contact and controlling the strike zone with a good measure of success.

He was never punchless to begin with but looks stronger physically now, likely just a matter of maturity when he got into his mid-20s. My impression is that his approach doesn't look like it has changed much, but the ball travels further now. Any readers who have seen Pollock play frequently, please share your observations, especially if you have seen any obvious changes in his approach over the last two years.

Fourteen hitters were drafted along with Pollock in the first round of the 2009 draft. The only one who has outplayed Pollock to this point is named Mike Trout.