Davis was born in Edina, Minnesota to Millie Davis and former major league pitcher Ron Davis.
Davis attended Arizona State University and played pitcher, first base and corner outfield. In 2006 he was named Pac-10 Newcomer of the Year, becoming the first freshman ever to lead the Pac-10 in RBI during the regular season. He also received First Team Freshman All-American honors. He was a three-time First Team All-Pac-10 selection and earned Third Team All-American honors during his sophomore season before becoming a unanimous First Team All-American during his junior year. He hit .353 in his college career, totaling 244 hits, 33 homers and 69 doubles. The 69 doubles is the fifth-most in school history.
Davis won the On Deck Circle Most Valuable Player Award in 2008, was a part of two Pac-10 Championship teams and went to the College World Series in 2007. He was also named to the ASU All-Decade team.
Davis was the 18th player taken in the 2008 Major League Baseball Draft, chosen by the New York Mets.
Davis made his debut at Citi Field on 19 April against the Chicago Cubs and singled in his first at bat. His first home run was hit on 23 April against the Atlanta Braves and traveled 450' onto Shea Bridge at Citi Field.