McMahon went 2-for-4 with a two-run home run and two runs scored overall in Wednesday's 11-8 loss to the Giants.
McMahon provided a two-run homer during the fourth inning to give the Rockies a 4-3 lead, but both teams continued the offensive barrage into the late innings. The 24-year-old has come alive in July with a .350/.381/.650 slash line and seven extra-base hits in 12 games.