Carlo Ancelotti's side currently sit five points clear of nearest challengers United following Sunday's convincing 3-0 drubbing of Arsenal at the Emirates Stadium.
But despite the Stamford Bridge outfit's imperious form - having conceded just eight goals in their 14 fixtures - Ivory Coast international Drogba, who took his tally to 15 goals in all competitions against Blackburn Rovers on Tuesday, says neither the Gunners nor Liverpool can be counted out at present.
And the 31-year-old also believes big-spending Manchester City - despite recording seven consecutive draws - and arch-rivals Spurs, 9-1 winners over Wigan Athletic recently, will also have a part to play come May.
"It's still too early to say that [it's a two-horse race]," he says in the January issue of FourFourTwo magazine, out now.
"I honestly think Liverpool can get back into it because we haven't played enough games to rule them out.
"Arsenal have always had lots of quality, but they're a lot more consistent this season, while Manchester City and Tottenham are stronger as well."
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The full, in-depth interview with Drogba, as well as further exclusives with Sergio Aguero, Luis Fabiano and David Silva can be read in the January issue of FourFourTwo magazine, available now.
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