The Spinks that beat Muhammad Qawi in 15 rounds, against Canelo at light heavy and catchweight. Spinks was 173 Ibs against Qawi for reference
Spinks fought as low as super middleweight earlier in his career, but that version of him wasn't near his prime, it made sense to include the prime version of Spinks when he was at 173 pounds at light heavy. He fought Holmes at almost 30 Ibs heavier.
Spinks is the only man in history to do what he did at LHW. Spinks is the only undefeated light heavyweight champion in boxing history. Something that can't be said about Tommy Loughran, John Henry Lewis, Billy Conn, Archie Moore, Bob Foster, or Roy Jones. In 101 years of crowning light heavyweight champion's, only one of them never tasted defeat while weighing 175 pounds, Michael Spinks. Spinks was also the first reigning light heavyweight champion to challenge and defeat the reigning heavyweight champion. Something past greats Billy Conn, Archie Moore, and Bob Foster all failed to do. Spinks the fighter was complete and could do it all. At 6' 2" Spinks was one of the biggest light heavyweight Champions in history. His fighting style is best described as being a boxer-puncher. He was a tremendous two handed puncher who could box and dictate with his jab and knew how to utilize his height and reach versus taller and shorter opponents. As he was forced to do in his Light Heavyweight unification bout with 5' 7" WBC Champ Dwight Muhammad Qawi, and against the 6' 6" hard hitting Gerry Cooney. His legacy was heavily tarnished by the one loss on his record: Mike Tyson. History should show that he was never off his feet prior and it took one of boxing’s hardest, fastest hitters ever to accomplish that knockdown and stoppage. Spinks would beat Canelo severely. Spinks. KO by round 9.