I don't know if that's a fair comparison because Marty no way in Hades starts a rookie QB in his actual first start just 15 minutes prior against the defending SB champs who have an ALL WORLD GOAT QB. Marty still goes with Brock Huard off the bench. But I get your point.
But when you really think about it, Mahomes damn near got beat by a rookie QB in his first start with very little or no 1st team reps notified of his starting just 15 minutes prior to the start of the game and you know Mahomes was thinking about this and it definitely motivated him for sure I assure you.
I think the Chiefs came in flat and when they found out the rookie was starting at QB they became even more flat. And you could definitely tell our o-line underestimated SD's defense for sure.
Just imagine IF James had played today.