McMahon is rated the club's No. 3 prospect and No. 64 overall, according to MLBPipeline.com. He was hitting .375 with 13 homers in 59 games at Triple-A, and he could offer the Rockies a powerful presence from the right side while Mark Reynolds deals with an injured left hand.
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In 48 games, Tapia had a slash line of .287/.341/.434 to go along with two homers and 10 RBIs.
Additionally, Minor League left-handed pitcher Sam Moll was designated for assignment.
Patrick Pinak is a reporter for MLB.com based in Miami. This story was not subject to the approval of Major League Baseball or its clubs.