I still can't see Oda willing to use Marco to hype King in a way of Marco getting defeated. Maybe Marco starts getting heavily beaten, and since Zoro already know Marco and also got helped by him to reach the rooftop, makes sense for Zoro to come and save Marco basicly in the same way Sanji did to Chooper.
And It makes sense for Marco to be heavily weakened, he gave his best to stall King and Queen at once (he didn't do nothing relevant to them tho, but bought some time), he used his stamina to heal lots of Samurai while Chooper was preparing the cure for Queen's vírus, while X-Drake and Hyogoro were fighting to protect him, and now hes fighting King, but i think he won't do nothing that much relevant to him either