He did fine for 30 minutes, dealt with Alvarez well, then Alvarez's superior experience told, he stepped back and dragged Sorensen all over the place. When you have a 6'4" 18 year old centre back who has come from Danish youth football straight to Serie A playing right back against a skillful winger as fast as an Olympic sprinter then he is going to be in trouble at times.
As soon as he got booked he was a liability then and had to be subbed but I refuse to criticise Sorensen directly as he has done a sterling job in the circumstances and will be an excellent defender if his early promise is anything to go by. I also won't pretend that it doesn't cause us problems at times, eventually you have to make a decision, you give young players more leeway but if you are in a desperate situation challenging at the top or bottom of a league it takes a brave coach to not automatically pick more experienced players, that's symptomatic of Serie A.
As it stands I don't see who we have that is any better, he'll grow into the team and when he does have games where he is really struggling, which inevitably he will have again in the future, then Delneri has a bench for a reason.