McMahon was optioned to Triple-A Albuquerque on Friday.
McMahon made a pair of starts and logged a couple appearances off the bench during his week-long stint with the big club, going 2-for-9 with a double, two walks and a strikeout. He figures to be back no later than Sept. 1, but an increase in playing time upon his return is not a given even with his .354/.401/.587 line at the upper levels of the minors this year. This move leaves Alexi Amarista and Pat Valaika as the Rockies' backup infielders.