Rangers icon Barry Ferguson has praised Celtic for securing the services of Joe Hart on a long-term deal but has warned his new team-mates to prepare for a verbal rocket.
The pair were colleagues for a season at Birmingham City in 2009/10 and it was the former England international's head-turning displays at St Andrew's that led him back to Manchester City.
Hart believes the switch to Parkhead has come at the right time for him as the 34-year-old looks to rebuild himself five years on from being axed by Pep Guardiola.
And Ferguson is convinced the signing of the shotstopper will be a major boost to Ange Postecoglou after a rocky start to the season.
Speaking to Go Radio, he said: "He trains to play, I know he hasn't played the last few years at Burnley then Tottenham.
"What Celtic are getting is a real presence in the goal, a real character.
"I played with him at Birmingham, all be it he was only 22, I was really impressed with him, first in in the morning and the last away.
"A very good trainer, a top goalkeeper, it's one of those positions you always make mistakes and it gets highlighted.
"Joe was the No.1 of England and Manchester City, Celtic have signed a top goalkeeper.
"When you have a big presence in the goal it helps you, he is very vocal as well, I think that's what Celtic need.
"That's the way Joe was at half time - even during a game, after the game, if you didn't perform well, he was more than happy to say his piece.
"I like players like that, I like players giving an opinion, and Joe was opinionated, I don't mind that."
