McIver managed Ballinderry to the 2002 All-Ireland Club title

McGonagle said members of the squad have been involved in "unacceptable behaviour" in recent years.

"It was behaviour, I thought I would never see in my lifetime," McGonagle told BBC Sport.

"Drink was an issue. Brian has got to stand by his principles because if you don't, you are on a slippery slope."

McGonagle was Donegal trainer for the majority of Brian McEniff's recent stint in charge of the county.

He is hoping that McIver's "northern mentality and focus" could help to get the most out of what is undoubtedly a talented group of players.

Former Derry forward Declan Bateson has described the new Donegal manager as "one of the best in the business".

Brian is tactically very astute and gets the best out of players Ballinderry clubman Declan Bateson

Bateson played on the Ballinderry team which McIver guided to the All-Ireland Club title in 2002.

"I've been managed by Mickey Moran, Eamon Coleman, Brian Mullins and Damian Barton and he is up there with the best of them," Bateson told BBC Sport.

"He is tactically very astute and gets the best out of players."

Bateson added that McIver's greatest strength is his ability to motivate players.

"He sees which players need an arm around them in order to get the best out of them and those who need a kick up the backside.

"He will need a good strong number two to keep him right because he is so focused and intense, that he can almost get too absorbed on occasions."

McIver, himself, says his task will be to turn a group of "very natural footballers" into a squad which plays "with great intensity and commitment".

"It will be a very big challenge to see whether we can harness that."