I think S2 is very natural and common, and that S3 is also acceptable, but I'm doubtful if I can use S1. I think it's strange, but someone says it's Ok even though it's uncommon, and Google shows me some sentences with this pattern. Is it acceptable?
S1. He is very confident to win the game.
S2. He is very confident of winning the game.
S3. He is very confident he will/can win the game.
Thank you very much.