The 20-year-old keeper reveals how he came to play in goal and explains how he is learning the tools of the trade from new coach Chris Woods and senior stars David De Gea and Anders Lindegaard.
Edwin van der Sar is nominated as an all-time hero in his position while Johnstone is also glad to see a number of his contemporaries getting the chance to shine in competitive football.
"There are a lot of good goalkeepers around," he stated. "They're also getting younger. It's good that teams are trusting and relying on young goalkeepers."