Butland represented Great Britain at London 2012 and was also a part of the England squad at this summer's European Championships despite playing only a handful of games on loan at League Two Cheltenham.
Foster said: "I've never seen a lad of his age with such ability - and that's including the people I've been with at Manchester United.
"I don't think we need to put too much pressure on his shoulders but he's a huge talent who's got absolutely everything.
"We need to calm it down a bit at the moment and help him keep his focus because he's got a big season coming up at Birmingham. But he will be a huge one for the future."
Foster himself is looking forward to the forthcoming campaign after making his loan move from Birmingham permanent in June.
He added on Sky Sports News: "Last year was great - I really enjoyed myself.
"I'm really happy with how it's gone, physically and mentally.
"I love my football and live for Saturday afternoon. I thrive on that pressure and look forward to it.
"But ever since I retired from England I've had a lot more quality time with the family and I'm enjoying it a lot more."