Barmby, 34, told The Sun: "The undoubted leader of Arsene's 'brat-pack' is Theo Walcott, who is already a full England player at 19 - and he wasn't even playing against the Blades.
"The performance of those lads took your breath away. They were brilliant.
"And it is the manager who needs to be commended for throwing a bunch of kids into a high-profile cup tie like that.
"It's terrific for the Gunners but, more significantly, it's fantastic for England's future."
He added: "Arsene took flak in the past for what critics saw as stunting the growth of English talent.
"He always said it was his aim to develop young English players and he's proved to be as good as his word."