Tbh the guys did really well. Spaletti didn't really have much choice, they were stretching us badly, it would be pointless to put on Ranocchia as the ball can bounce anywhere within the box defending crosses, so it would certainly be more effective shutting them down out wide rather than dealing with it in the center.
So subbing in Santon made somewhat sense, the only other alternative would be Dalbert.
You don't put Karamoh on when you are defending with a man down, he's not the type to put in the defensive effort like Perisic and Candreva.