Cheltenham's Scott Brown spent three months as second-string stopper to Butland while the Blues youngster was on loan at the Robins earlier this season, and worked intimately with the starlet on the training ground.
And that time spent together has helped convince Brown, a veteran of almost 150 Football League appearances, that the teenage keeper - who is already number one at Under-21 level - is destined for big things.
"Jack will go on to play for England, I'm pretty sure about that," he said.
"When we were playing up at Accrington on a Friday there were members of the England staff up there and I'm pretty sure they weren't there just to watch the game.
"He's a good keeper and he will only get better."