He played in Major League Baseball (MLB) for the Arizona Diamondbacks, San Francisco Giants, Chicago Cubs, Seattle Mariners, Toronto Blue Jays, and Miami Marlins.

For West Linn, Gillespie was a three-year letterman and won All-State honors as a shortstop and was also a standout pitcher.

Gillespie also competed in football and basketball at West Linn, and later attended Oregon State University.

After redshirting his freshman year at Oregon State, Gillespie won the Most Improved Player award his junior season and then later became a captain of the team.

As a senior captain, Gillespie helped lead the Beavers to the 2006 Division I National Championship over the North Carolina Tar Heels and was also named the Pacific-10 Conference Player of the Year.

[3] In late July 2009, he was traded to the Arizona Diamondbacks with Roque Mercedes for Felipe López and assigned to Triple-A Reno.

He was activated on July 14, and got a pinch hit single that night in the eighth inning against the St. Louis Cardinals.