Alternate history: Jeff never comes out of retirement, instead Johnson faces a certain aging thongdonner which was actually a fight that was almost made. I highly doubt he wins in any realistic scenario, but could Corbett have made a better account of himself than Jeffries did?
He couldn't have done much worse! Realistically he might have dodged about for a few rounds and landed some ineffectual punches but no ,he wouldn't have. Jeffries only lasted as long as he did because Johnson was enjoying himself too much repaying old scores and slights to go after Jeff earlier.
My guess is that any proposed Johnson - Corbett fight was all bluff on Corbett’s part. Corbett being a dirty four flusher as they used to say. Lol. Jim was only good for spitting venomous racist comments at Johnson whilst in his “safe” role as Jeffries cornerman. Even Jeffries told Corbett to shut up at one point - because it was Jeff, NOT Corbett, taking Johnson’s reactive and damaging punches. As Mac said, Jimbo possibly couldn’t do much worse and while Johnson most certainly did carry Jeff, Corbett still wouldn’t be able to cope with any where near the punishment Jeffries absorbed before going down. Man, IF Corbett only did have the balls to get in there with Jack - Johnson might’ve relished the beating he would’ve given Corbett more than the one he dealt out to Jeffries. Bar Sullivan, a W over Corbett would’ve seen Johnson beating 3 of boxing’s earliest and highly revered Champions. In fact, I think Corbett would’ve done worse - I don’t think even Johnson, as hard as he tried for illusory effect, could manage to reliably carry Corbett for as long - with Jim folding irreparably early in the fight - possibly even opting out by way of a dodgy self DQ.