Manchester United have struggled since Ferguson’s retirement in 2013, with David Moyes and Louis van Gaal both failing to challenge for the title in the interim.
Jose Mourinho took charge in the summer and Ferguson said the Portuguese has the ability to rival Pep Guardiola, but results have been mixed and United are currently seventh, six points behind City, Arsenal and Liverpool.
Ferguson told the German magazine he thinks City remain the most likely champions, despite a run of six games without a win in all competitions, but said: “It’s harder to predict than it was for many years.
“I think there’s five potential candidates: Manchester City as favourites, Tottenham and Liverpool, but also Man United are still there if we get some consistency soon. Even when you are trailing by six, eight points, it’s still possible to catch one or two teams.
“The rivalry and the experience of Guardiola and Mourinho makes for an exciting competition. And you shouldn’t forget Arsenal. The team is more sturdy. They’ve got better and more aggressive. I’m impressed with the young boy Alex Iwobi.”