[1] In a 1976 match between the USSR and the United States, Tubbs lost by knockout in the second round to future Soviet Heavyweight Champion Igor Vysotsky.

[citation needed] In the match-up meetings USSR versus the United States Tubbs defeated the two-time amateur European champion Yevgeni Gorstkov and the future silver medalist of the Olympic games Pyotr Zayev.

Among his other notable Amateur victories were defeating James Broad and Jimmy Clark, and 1980 Olympic bronze medalist Stephen Left.

[citation needed] As an amateur, Tubbs worked as a sparring partner to Muhammad Ali, helping the former to prepare for his rematch with Leon Spinks for the World Heavyweight Championship.

[citation needed] On November 21, 1989, Tubbs out-pointed top contender Orlin Norris, winning the North American Boxing Federation title.

[citation needed] On April 20, 1991, a 34-year-old Tubbs lost a highly controversial ten-round decision to future Undisputed World Heavyweight Champion, Riddick Bowe.

Tubbs came back to out-point future WBA Heavyweight Champion Bruce Seldon, knocking him down in the 1st round, and the undefeated Alexander Zolkin, but then suffered another first-round knockout—this one to clubfighter Jimmy Ellis.

[citation needed] In December 1993, Tubbs took part in the one-night People's Choice Heavyweight Tournament in Bay Saint Louis, Mississippi.

He knocked out Willie Jackson in the first round and won three-round decisions over 1984 Olympic Gold Medalist Tyrell Biggs, Jose Ribalta, and Daniel Dăncuţă to win the tournament.