As the midfielder celebrates his birthday, Postecoglou hopes that he can count on the all-action star even more in the coming months.
Bissouma was suspended for a game after filming himself inhaling laughing gas.
Postecoglou told reporters: “I don't want to be too flippant about it because we've said all along this is about trying to guide Biss so he becomes the best version of himself, both on and off the field. There's no doubting his qualities as a player.
“From the moment I arrive, every time he's been fit, he's played. That's how highly I rate him. But at the same time, we feel there's areas of his game he can improve, just around his discipline, his positioning, the way he plays the game.
“There's a correlation to off-field as well. He's been really focused since the incident. I think him not playing that first game really hurt him as it should. You can fine players but when they don't play, they feel it more. He doesn't want to be in that position again.
“He knows that not just for himself but for the whole group, we need him to be at his best so he can contribute to the team and he'll only do that if he continues to show the same focus and discipline that he has.”