Speed, 39, who played 640 top-flight games, was in the Sheffield United team beaten 6-0 by the young Gunners in midweek.
And he said: "This is the best group of young players I have ever seen.
"I have seen a lot of young players come through over the years, but Arsenal were above anything I have seen. They were excellent.
"It has come to fruition now. I was 23 years older than one of their players! And I felt it at times."