The Finn was outstanding for the draw at Southampton on Saturday.
"Jussi came to us from Bolton having only played about 15 games for them the previous season, 2011/12, having got injured before Christmas and not been able to get back into the side," Margetson told whufc.com.
"It's been great working with him and I feel as though we're going to kick on again. He played every single game for us last season which, having taken in someone a bit older, was superb, as were his effort and application.
"Credit to him, because you can't stay in the game as long as he has at this level without the attitude and professionalism that he has shown.
"He gives 100 per cent in everything he does, on the grass and in the gym, which helps with prevention of injuries and different things."