"I think some of the decisions we had last season were abysmal," said Celtic.
On his desire to see his players question decisions and support each other on the pitch, said: "I did it myself as a player, not to influence the ref but to let him know we weren't happy.
"Any challenges that were a wee bit heavy, there were two or three of us around the player who did it.
"There was a togetherness and I want to see that again. I want to see them sticking up for each other.
"They did that in the last few games. That's what teams are about - looking after each other on the pitch and having a good spirit off it."
The Celtic manager added: "It's important; it's a basic thing in the game and it's difficult because in the modern game you've got all these different coaches. But we'll try to develop the players and make sure there's an affinity with the club."
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