At one stage earlier in the season, Jose Mourinho's men held an eight-point advantage over their rivals.
That was after Chelsea had made an imperious start to the campaign, while City's stuttering early form sparked talk of a comprehensive romp to the title for the men from Stamford Bridge.
However, six straight league wins for City and a draw and a defeat to Sunderland and Newcastle United for Chelsea means the gap between the top two is now down to three points.
Docherty, who managed Chelsea between 1961 and 1967, guiding them to League Cup success in 1965, believes his former employers will just have the edge.
"It'll be them or Man City. I think it'll be Chelsea," he told Perform.
"I'll be amazed if the champions don't come from Chelsea and Man City. It's a two-horse race.
"City at full strength and Chelsea at full strength... it could be a point in the championship.
"They [Chelsea] won't run away with it. I wouldn't be surprised if they won it, and I'd love Chelsea to win it actually, but they won't run away with it, it'll go right to the wire."
Docherty lauded the qualities of Manuel Pellegrini's side, and said that Chelsea's recent slip-ups are nothing more than a sign of the unpredictable nature of the game.
"City are fantastic to watch, they're an absolute joy to watch playing football," he said.
"That's the great thing about football. There's no such thing as a sure thing.
"You go on a fantastic run of victories then you play someone you should beat quite comfortably.
"All of a sudden, football being football, you get beat and it's how quickly you recover from a shock defeat and get winning again."
