David Moyes has struggled since succeeding Ferguson at Old Trafford in the summer. The Red Devils lie seventh in the table, six points outside the top four and a further eight behind leaders Arsenal.
Their penalty shoot-out defeat to Sunderland in the Capital One Cup semi-finals in midweek means they are also out of both domestic cup competitions, but Ferguson remains upbeat about the prospects of a team he now enjoys watching as a supporter.
"I'm not writing anyone off," the 72-year-old Scot told BBC Sport.
"Tottenham have started coming forward a bit now, Liverpool are doing very well, Everton are doing very well, (Manchester) City are doing fantastic and Arsenal are top of the league.
"With Jose (Mourinho) you expect (Chelsea) to win games playing ugly, but all these teams are in there. United are in behind chasing."
He added on Sky Sports: "United can do anything. They have got that great philosophy and history, they will always do well.
"I can watch the team whenever I want and I've really enjoyed it. I'm going as a supporter now and instead of suffering with the team, I'm suffering or enjoying it with the fans. I'm really enjoying watching the team play."