McLeish suspended midfielder Barry Bannan earlier in the week after he was arrested on suspicion of drink driving and bailed by police last weekend. Bannan is not available for Saturday's game at Sunderland and no timescale has been put on the length of his ban.
When asked why he had suspended Bannan, McLeish said: "We have to have discipline - but I'm not going to add to the statement that was made previously. There is nothing to add."
He added: "How long will the suspension be in place? We'll just have to wait and see but he is not available this weekend.
"We are not pre-judging anything at all and have made that clear.
"Barry has done well this season but he can get better, like everybody else.
"I don't want to speak about Barry anymore. We are concentrating on the game against Sunderland and I'd prefer to talk about that."
But when asked about discipline as a general subject, McLeish said: "I think that we have to have a bit of mutual respect. We're in the professional world and there have to be certain ground rules.
"I'm not saying it's anything to do with last season (at Villa) because you can never tell. I didn't base it on last year, I based it on what I feel is right.
"It happened with me as well in previous clubs. We can get along fine but you've got to have discipline. The senior players can help the youngsters and be a big influence in every respect."