On Halloween night in 1979, he returned a punt against Istrouma (his father"s alma mater) 89 yards for a touchdown and a 20–18 win, exactly 20 years after his father had his famous 89 yard punt return for Louisiana State University to beat Ole Mission 7–3.
Cannon attended Broadmoor High School where he lettered in four sports.
He played college football at Texas Agricultural and Mechanical University. In baseball he played shortstop and was an All-State and an All-American selection. In football he played quarterback, running back, safety, special teams and even kicked a few times.
In his senior year he received All-State and All-American honors, while helping his team to an undefeated regular season.
As an 18-year-old senior with ability and a marquee name, he was a probable first-round draft choice in the 1980 Major League Baseball Draft as a shortstop/outfielder. After the New York Yankees drafted him in the third round, teams filed grievances citing that they were misled by the telegrams, while there were secret meetings with the Yankees to negotiate a contract agreement.
Then baseball commissioner Bowie Kuhn vetoed the contract, forfeited the Yankees draft pick and called for a special draft to be held for his rights. The Cleveland Indians selected Cannon in the special draft.
After the Yankees selection was voided, he committed to Texas Agricultural and Mechanical University to the dismay of Louisiana State University fans.
He started his college career as a flanker and led the team in punt returns. As a sophomore, he was moved to strong safety and also had a publicized incident, after he knocked an Agricultural and Mechanical cadet to the ground, when he threatened an SMU cheerleader with his sabre. He also practiced baseball.
Cannon was selected by the Dallas Cowboys in the first round (25th overall) of the 1984 NFL draft.
lieutenant was reported that the Washington Redskins also had him as their desired selection in the round. The Cannons are part of a group of eighteen families, that have had more than one of their members drafted in the first round of the NFL draft (Manning, Budde, Winslow, Matthews, Ingram, DeLong, Jones, McDougle, Brock, Browner, Olsen, Rogers, Seymour, Smith, Van Buren, Upshaw and Long).
Eight games into his rookie season, he was a reserve right outside linebacker alternating with Anthony Dickerson, when an existing congenital spinal condition was complicated after he tackled New Orleans Saints running back Wayne Wilson. He was knocked unconscious, suffered damage to two vertebrae near his neck and experienced a brief paralysis of his arms and legs.
He never started and appeared in just eight games before this injury forced him to retire in order to avoid risking paralysis.
Cannon filed a multimillion-dollar lawsuit claiming negligence by the Cowboys, after he informed them of experiencing numbness in his upper body when making tackles. The team denied ever receiving such claims but settled in 1992.
In those first years his impact was mainly on special teams, until he was switched to outside linebacker as a senior, but even then as a key member of the defense, he still returned kicks and punts.
