England head coach Eddie Jones watched from the stands ahead of their opener against Scotland on 6 February.
Sarries are playing in the Trailfinders Challenge Cup to be ready for the start of the Championship season on 6 March.
They were relegated last season because of persistent salary cap breaches.
"I thought Billy was outstanding, genuinely. He has been brilliant with this young group all week. He has been really positive with them," McCall said.