Dude, Perospero must have other attacks, even Marco got scared by Perospero aiming at him, with Big Mom's assistance. Im not saying Perospero will be the one to almost defeat Marco, he will significantly hurt/distract Marco so King has the opportunity to land a clean hit, heavily hurting Marc, thats all. And it's not bad, Marco doesn't have to stay out for the rest of the arc, even if he does he already did pretty well even in complete disadvantage