Postecoglou's arrival has been welcomed by McGregor who is currently with the Scotland national team.
“A new manager coming in will always have his own ideas on the way he wants to play football, and the way that he sees football – how people act around the building, what he wants his team to look like – so it’s a clean slate for everybody, and we just need to come back and try to impress as much as we can in training and in the games when we get the chance as well," he told the Celtic website.
“With the new season coming around, everybody wants it to be successful but we know that the hard work starts as soon as we get back into pre-season. That element is absolutely vital and very important to having a good start in the season.”
McGregor is aware of the responsibility he and James Forrest will have in helping the transition to a new manager.
Their Scottish football experience will also be vital to Postecoglou, who made a Kenny Dalglish poster revelation, getting his feet under the desk. who will be experiencing Scottish football for the first time.
“In football there are so many approaches and styles of football, and when you meet a new manager, you’re always open to learning new things and what he sees the game looking like,” he said.
“He’s there to help you and you’re there to learn from him as well, so that’s the exciting part of meeting new people in football.
“He’s coming from a different continent and it maybe falls on the likes of me and James who’ve been at the club for a long time to try and help, and know what’s around the corner in terms of games, and we’re obviously happy to do that and work together.
“But he’s a smart guy, he’s had a really successful career as a manager so he’s going to have huge amounts of knowledge anyway.”