Walker was called up from Triple-A Reno on Friday.
Walker has played in 17 games with the Diamondbacks this season, going 3-for-17 with two RBI and 10 strikeouts during his brief opportunities at the big-league level. He will supply a little extra depth all around the field but don't expect him to make much of an impact. Jimmie Sherfy was optioned to Reno in a corresponding move.