Hansen wrote in the Telegraph: "David is a top-class manager, one of the very best, and there is no way that anybody in his position would ever dream of turning down a six-year contract to manage Manchester United.
"But I believe he would have been better served had he taken the job on with a different United team to the one he inherits from Ferguson.
"Ferguson has been unbelievably clever in recent weeks by telling the world that United are in the best position they could possibly be in, with the current squad ready to prolong the success he has masterminded for the last 20 years. But after saying all of that, he has then gone and announced his retirement.
"He has set the scene for the future, but outside of Old Trafford, people are wondering whether this group of players he has left behind really are capable of dominating as Ferguson’s team have done in the past.
"United have greater strength in depth than Manchester City and Chelsea and they remain the best when it comes to winning when performing poorly. That is why they won the Premier League by some distance this season.
"But I believe City and Chelsea have stronger starting line-ups than United and, if they kick on and add to their squads this summer, they will pose a much sterner test next season and make David Moyes’s first campaign as manager a much more difficult one."