Born and raised in East Hampton, Connecticut, Pollock attended East Hampton High School in East Hampton, Connecticut. At East Hampton High, Pollock was a four-year letter winner as a shortstop, played varsity soccer as a freshman, and was a member of the National Honor Society. Pollock was Gatorade Player of the Year in Connecticut, receiving the most votes for a Connecticut player since 1974, and was also named state player of the year in 2006 by the coaches association. As captain of the team, Pollock batted .562 and also held a 0.62 ERA as a pitcher, leading East Hampton to four conference titles and three state title.
Pollock playing for the Reno Aces, triple-A affiliates of the Diamondbacks, in 2012
Pollock was called up to the majors for the first time on April 18, 2012 and made his debut that day. Batting as a pinch hitter for Justin Upton, Pollock collected his first career MLB hit, a single, on April 23 against the Phillies. He would play in 31 games that season for the Diamondbacks, batting .247 with 2 home runs and 8 RBI.
In 2013 Pollock batted .269 with 8 home runs and 38 RBI over the course of 137 games.
Pollock missed the second half of the 2014 season with an injury. Up to that point in the season, he was batting .302. In 2015, he was named a National LeagueAll-Star.