Henry and Szczesny spent a brief spell together when the former returned to the Gunners on loan in 2012.
He told Foot Truck: “The best player in Arsenal's history. The best player in Premier League history.
“He was very demanding, especially on the youngsters.
“The guys always said they were afraid of him in training.
“When you failed a pass, he got p***ed and let you know he's not happy with you very vocally. Great guy."