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.
"From what I've seen, he's going to be really good one day," said Story, who hit with McMahon daily during the offseason. "He's a hitter. He might've struggled this year a little bit, but I struggled too in Double-A when I first got there."
Story only hit .200 with 82 strikeouts in 237 plate appearances in his first season in Double-A when he, like McMahon, was 21. However, when he played in the AFL, he changed his approach and saw a major improvement with a .256 average and 11 extra-base hits in 22 games.
"It was huge for me," Story said. "I come to the Fall League and made some changes, and that's stuck to where my routine is today. It was good competition, so it's a good competition for guys to see how they stack up against the best guys in the Minor Leagues."
The following season, Story hit .279 with a career-high 20 homers between Double-A and Triple-A Albuquerque. Now he's become one of the best shortstops in the game, leading the National League with 27 homers on July 30 when a UCL tear in his left thumb curtailed his season.
Story sees how McMahon can follow a similar path.
"I would expect him to have a very good Fall League and show his talent," Story said.
Ben Weinrib is a reporter for MLB.com based in Denver. This story was not subject to the approval of Major League Baseball or its clubs.