[8] DeMarco was named to three Pro Bowls (1963, 1965, 1967) and one Associated Press (AP) first-team All-Pro team (1967) while playing for the Cardinals.
[9] Early in their careers, McMillan and DeMarco served in the military together, and soon after became roommates with the Cardinals, a rare interracial pairing at the time.
[10] The Cardinals released DeMarco after the 1969 season, after a dispute with head coach Charley Winner,[7] and he soon signed a contract with the Miami Dolphins, choosing them over the Pittsburgh Steelers.
[12][13][8] In 1972, when future hall of fame coach Don Shula made Jim Langer the starting center during the preseason, at the suggestion of offensive line coach Monte Clark, DeMarco left training camp for a time as he did not believe he would receive a fair chance to compete for the starting job.
[8] After retiring, DeMarco returned to St. Louis, where he worked in electronics and finance, and was a long-time salesman for a chemical company.