Chelsea currently lead the Premier League by five points
The Blues face City at Stamford Bridge on Saturday in what is already being billed as an early title decider.
Victory would see Jose Mourinho's men stretch their lead at the top of the table to eight points with 15 games remaining.
But Sinclair is wary that City possess the talents to claw back a large deficit and that Chelsea must not slip up at any point between now and May.
"It will be a tough game, but on the back of a great win in midweek, I would fancy Chelsea to get the result against Manchester City," former Blues defender Sinclair told the Press Association.
Chelsea v Manchester City - Premier League Preview
"As for the title, Manchester City have already pegged back a nine-point lead earlier in the season, so all it takes is for Chelsea to have another blip and all of a sudden City are back in the ball game.
"However, if Chelsea do win on Saturday, then you would not bet against them going on to win the championship with that advantage."
Chelsea drew 1-1 with City at the Etihad in September, where Blues legend Frank Lampard scored a late winner for the defending Premier League champions.
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