Both Shaw and Mclean were strong, rugged guys, but they couldn't make it in boxing, if i remember rightly Lenny got knocked out twice in the first round against a journeyman pro.
Very aggressive guys at that level, both used to take a ton of cocaine before fights which added to that aggression. Shaw was a smaller guy and by the time of their fight Lenny had juiced up to about twenty stone, he got caught rushing in and ate about fifty punches.
Both were glorified brawlers with below average boxing and zero grappling experience, they wouldn't make any impact.