Ferguson announced his retirement plans at Manchester United yesterday.
McLeish, Ferguson's former captain at Aberdeen, told the Scottish Sun: "The challenge for whoever comes in will be to surpass his achievements. Personally, I can't see it happening.
"That wouldn't stop Davie, he wouldn't be slow in going through that door if he got the chance.
"He has great longevity in the Premiership and he's proved himself in that league with the very best of them.
"His budget has never been able to match the bigger clubs. When he did get money to spend he invested it wisely in Marouane Fellaini."