Coach Magnus Norman says that although Stan Wawrinka just won his second Grand Slam title at Roland Garros, he remains unpredictable from week to week.

The 30 year-old Swiss is now ranked No. 4, one spot off his career-high mark, earned when he won the 2014 Australian Open. “He’s a very interesting player to watch, because you never know what to expect,” Norman told a group of journalists at the Fench Open. “This week we saw the greatness of Stan, but next week it could be something else.”

The Swede, who reached the Roland Garros final in 2000, said it was a big step for Wawrinka to get through the first week in Paris. Last year, Wawrinka lost in the first round against Guillermo Garcia-Lopez. This year, he defeated Roger Federer in straight sets in the quarterfinals and upset world No. 1 Novak Djokovic in the final.

“Every day he has been putting in the work and every day I have been really happy when I have gone to bed,” said Norman. “But, going into the tournament, I felt that if he could get through the first couple of rounds he was going to be dangerous and a contender. But I never believed it until maybe the first match point. It was, like, ‘Now he has a chance to win it.’”