I feel that the first sentence above is very astute. If a boxer cannot hurt Frazier sufficiently to keep Joe away, then they are inevitably doomed. (Ali being the exception, imo) I think Walcott would have very fortunate to make it to the 10th round against prime Frazier. It might well be over by the 7th.
Walcott is more than crafty enough to take it the distance, but at some point, Frazier gets a few 10-8 rounds by way of the overhand left hook and wins a close decision - 143-140 / 8-7
For some reason I see Walcott really troubling Frazier, at least until later on... Walcott can be slick, he hits plenty hard enough, and he clinches appropriately, which would be a main factor in his getting offense off while stopping Frazier's rhythm. He did it well against Marciano, and I think it would serve him well against Frazier as well. Like most others, I think Frazier grinds him down and ends up putting some clean and pivotal punches together to score a knockout, somewhere around 12.