McMahon headlines the group of seven Rockies prospects who will play in the AFL for the Salt River Rafters this October and November. McMahon will join pitchers Shane Carle, Rayan Gonzalez, Sam Moll and Jerry Vasto along with infielder Pat Valaika and outfielder Noel Cuevas. Moll, ranked 21st, is the only other player among the Rockies' top 30 prospects.
McMahon, splitting time between third and first base, was hitting .242 for Double-A Hartford after batting .300 for Class-A Advanced Modesto last season. However, his bat is still full of promise as his above-average power has produced double-digit homers in all four of his professional seasons.