In 2007, McMahan was with the New York Giants. He led all Giants receivers in the final 2007 preseason game against the New England Patriots on August 30 with 57 receiving yards. McMahan was released by the New York Giants a few days later in September 2007. He was added to the practice squad about two weeks later. He remained with the Giants' organization until the beginning of October 2007, when he was released.
One week later, the Kansas City Chiefs signed McMahan to their practice squad, but only a week later, McMahan found himself, once again, released. In May 2008, McMahan, once again, signed with the Chiefs. He was cut after the Chiefs last pre-season game in 2008.