Holmes also changed his style and approach radically for his 1990s comeback, admittedly drawing from the Foreman template.
In 1988, Don King showed up on his doorstep with THREE MILLION DOLLARS to fight Tyson on short notice, so Larry, knowing at age 38 he had neither the time to train properly or opportunity to shake off 18 months of retirement accumulated ring rust with a tuneup or two, took the cash. To his eternal credit, Holmes did not lie down quickly against a peaking Mike, or quit with the kind of pocketed multimillion dollar guarantee Duran already secured in New Orleans for SRL II. He made an honest effort, actually won a couple rounds against one of the fastest starting heavyweights in history, and did better than many noteworthy Tyson victims.
For his return in the summer of 1991, he now took the time to train properly, adapted to the reality of being in his 40s by not using his legs so much, and extended himself with a pair of ten round shutouts against veteran trial-horses (specifically Eddie Gonzales) before the year was out, ahead of the Mercer surprise.
Yes, he was three and a half years older for Mercer than Tyson, and ten pounds heavier, but he was far better prepared, no longer rusty, and no longer trying to box on his toes as if he was in his 20s. The Tyson of 1988 would have experienced considerably more headaches with the active, smarter and better trained Holmes of 1992 than the rusty, misfiring and age unadapted version who fell in four rounds. (As soon as Larry went to his toes to start that fatal stanza, with hands at his sides, Michael Spinks immediately started screaming from the fourth row, "What are you doing? Concentrate! Concentrate! Jesus, what are you doing?" The wiser and better trained sage who schooled Mercer would never have made that kind of mistake.) Holmes shed 30 pounds in short order for Tyson, a strain he spared himself of for his 1990s comeback. Mike would still beat Larry, but not that quickly or easily.
As for Tyson's best win, I'm actually partial to Tyrell Biggs these days. Mike was at the peak of prime competitive preparedness and experience, and keyed his hook with body shots to wear Biggs down with attrition, after quickly taking Tyrell out of his fight plan. Maybe Tyson was better for some much briefer knockouts, but here's an instance where Mike was firing on the most cylinders for an extended number of rounds against a primed opponent. I suspect he started going backwards with the five briefer defenses he had prior to Douglas in Japan. I can't see Tokyo Buster prevailing over the Tyson of the Biggs fight, who took away Tyrell's legs with body shots, jabbed as an effective diversionary tactic, and did not rely on a single big punch to win, but methodically pounded down an athletically primed guy with a then solid chin, as Mike had uniquely done to Pinklon Thomas earlier in 1987.
Tyson claimed he could have wiped out Biggs at anytime after round three. Mike would have been well served by practicing wearing down other failed challengers like the chinny Carl Williams with that same body attack prior to Douglas. Why didn't he after Biggs? Well, one possible hypothesis is that Tyson-Biggs was the final HW Title fight scheduled for the Championship Distance, eliminating the Championship Rounds impact of such a body punching. Mike himself might be the best guy to ask about this, but early rounds could never again be conceded on cards against the payoff of a later round rally purchased by steady body punishment, not with just 12 rounds scheduled as opposed to the championship distance. (Tyson only lost the opening round to Tyrell, but if Biggs had somehow managed to carry out the plan mapped out for him, Mike's body blows still would have eventually taken away his legs and paid off late. This match showed the proper direction for Tyson to move in if he was to continue improving as a fighter.)