Chelsea returned to winning ways at the weekend with a hard-fought 4-2 victory over Watford at home.
The result ended a three-game winless streak for the Blues which had seen them fall behind early pace setters Manchester City and Manchester United.
The gap to the top currently sits at nine points but Cahill is confident the Stamford Bridge club can eat into it.
And the Blues captain has predicted both Manchester clubs will slip up with some difficult fixtures ahead.
“Last season we were eight points behind Man City and we managed to claw it back,” Cahill said.
“I’m not saying it is going to happen, but we need to calm down and get back to it.
“We are champions of last season, in the middle of October, there are loads of games to play.
“Man City have loads of tough games to play, Man United and everyone else have massive games to play. I still think it is open.”
However, Cahill did admit if City keep up their early-season form throughout the campaign then they will be deserved winners.
“If Man City keep smashing people, then they are going to go on and win the league deservedly,” he added.
“It is difficult to maintain it for such a long period and if they do – or whoever does do that and it was us last year – they deserve to win the league.”
Chelsea are away at Bournemouth next weekend, with City travelling to West Brom and United at home to Tottenham.