Foster spent five years on the Old Trafford payroll before leaving for Birmingham in 2010.
And although that period included two seasons out on loan and another sidelined by injury, he still got a pretty good insight into what makes the mighty Old Trafford machine tick.
Foster accepts the heat is on Moyes following Ferguson's exit.
But he is confident United have the right man for the job.
"David Moyes has huge shoes to fill but I don't think anyone could have walked into that job and felt no pressure at all," he said.
"It is the biggest job in world football.
"United have made a good decision. Moyes has got that steel about him.
"From what I hear he is a hard character. He has high standards all the time.
"You see what he has done at Everton on a limited budget. He has eked out the last little bit of quality from every one of his players."
It might not be easy though.
Quite apart from having to stamp his authority on a dressing room used to winning the trophies he has never collected, Moyes also has to brace himself for a summer spending spree from fellow Champions League contenders Manchester City, Chelsea and Arsenal.
Europe is also a priority after two poor seasons by the Red Devils high standards.
Yet despite these obvious challenges, Foster expects his old club to keep on winning.
"United will always carry on the same," he said.
"They are very good at signing players who believe in everything they stand for.
"It is football, football, football. It is winning at all costs. It is the way they are.
"I am sure they will keep the old heads around, even when they retire.
"Paul Scholes and Ryan Giggs will always have some input and some sort of say just to drive home the message to the new lads.
"It is bred within them to be winners and that will always be the case."
Foster only made 23 first-team appearances at United, largely playing understudy to Edwin van der Sar.
He has since suggested the sheer intensity of life at Old Trafford was somewhat overwhelming.
But he would not swap the experience for anything.
"I am really proud to have played at a time where I could work for manager the likes of which you will never get again anywhere in the world," he said.
Foster was equally proud to have been part of Ferguson's final game, even though he did concede five times in the highest-scoring draw in Premier League history.
The 30-year-old was going to grab a quick word with his old boss afterwards.
In the end though, he decided it was not the greatest idea.
"When we were in the tunnel everybody, and I mean everybody, wanted something from him, either a photo or to shake his hand," said Foster.
"I just left him to it. He has had a fantastic career and taking part in his final game is something I will remember for a long time."