Man Utd legend Robson impressed by Arsenal youngsters
"I think they are a very good side," the Blades boss said. "They've done well in this competition for the last few years because they're not just about passing and movement, they are a physical set of players as well.
"You have got to have that bit of balance within your team - strength and pace as well as passing and possession, and that's where Arsenal are as good as any team I have seen.
"The movement and the protection of the ball is excellent and that's why they are such a good team."