Long was the starting quarterback for the New Mexico Lobos football team from 1969 to 1971, recording consecutive winning seasons and earning player-of-the-year honors in the Western Athletic Conference (WAC) in 1971. His professional career began with the BC Lions of the Canadian Football League (CFL) in 1972, with which he played 68 games in total. In 1974 he departed to the Detroit Wheels of the World Football League (WFL). That year he intercepted three passes for 38 return yards, and returned 20 punts for 217 yards and 14 kickoffs for 402 yards. He returned to the Lions for three years and had one of his best years in 1975, when he intercepted a team high eight passes for 88 yards. A Western All-Star in 1977, Long also led the team in punt returns in his last three years, and is still the fourth leading all-time returner, with 1946 yards on 192 punt returns, with one touchdown.
Long returned to New Mexico as the head football coach on December 20, 1997. His overall won-loss record was 65–69 in 11 seasons. His 65 wins are the most of any head coach in program history. Long surpassed Roy W. Johnson's mark of 41 wins during the 2005 season.
Long led the Lobos to three straight bowl games from 2003 to 2005, a first in program history. The Lobos been bowl-eligible for seven straight seasons, from 2001 to 2007, another program record. This streak continued into the 2007 season as the Lobos accepted a bid to the New Mexico Bowl, where Long garnered his bowl win with a victory over the Nevada Wolf Pack.
After 11 seasons, Long resigned on November 17, 2008, two days after the Lobos' regular season ended. Long cited that he was not the right person to lead the program to newer heights. He added that he had no plans of retirement, and that he wanted to continue to coach as a coordinator. In 2011, he was promoted to head coach at San Diego State after two seasons as their defensive coordinator.