He told the Scottish Sun: "Islam is a brilliant player and that game against Switzerland showed exactly why Chelsea signed him.
"The three goals he scored that night at Falkirk Stadium were different class.
"You can see he is an outstanding performer in training.
"He is not the biggest but is strong and quick. He's quick with the ball and has everything a striker should have.
"He is a really good player with a bit of that Scottish cockiness as well.
"If he keeps playing the way he did in the Euros then he has a very big future ahead of him."