Moyes succeeded Ferguson last summer and has found the task challenging, with the team that won the Barclays Premier League last May unable to mount a sustained challenge this term, even for the Champions League places.
But the former Everton boss has suggested any manager, even Ferguson, may have struggled with the squad he took on, given the age of many of the players.
United's squad includes a number of players aged over 30, including centre-backs Nemanja Vidic and Rio Ferdinand, left-back Patrice Evra, midfielders Ryan Giggs and Michael Carrick, and striker Robin van Persie.
"People are aware there is a squad that is a bit more ageing, so I think it would have been a tough season for whoever was in charge of Manchester United this year," Moyes told national newspapers.
"And I actually think if Sir Alex was here this year it would be difficult for Sir Alex as well and I'm sure he would be aware of it.
"It could have been the case no matter what this season, but it has been so un-Man United, which is why we have to look to continue a policy of building, improving, getting better and that's what we'll try and do."