The current champions have taken 13 points from a possible 15 in their matches against fellow contenders Chelsea, Arsenal and Liverpool. Second-placed Blues have managed just five from 15, the Gunners six from 18 and Rafa Benitez's men only four from 18.
Fergie said: "I said results between the top four would be the key this season and that's been proved right.
"Thank goodness we've performed well and got results against our main rivals, because we've dropped points elsewhere.
"The Premier League has become much tougher in recent seasons. For example, we lost six points to Manchester City this season, which is something we didn't expect.
"We also lost at West Ham and Bolton, but the key is keeping those setbacks to a minimum.
"We've managed to do that and if we can win our next two games, then we'll be champions."