Manchester United are currently 11 points ahead of Chelsea, who have a game in hand following their visit to Japan for the Club World Cup.
The Blues began the season in fine form before falling away, but Cahill believes Sir Alex Ferguson's team can be caught after they were held to a 1-1 draw by Swansea City.
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"They are a very strong outfit and have been there many, many times, so it will be tough, but all we can do is try not to drop many points now and with performances like that we won't go far wrong.
"Obviously it is a big gap but we can only go out and get results."
Chelsea had seven different scorers in the demolition of Paul Lambert's side as they equalled their biggest winning margin in the Premier League era.
And Cahill hopes that Rafael Benitez's men have sent a message to the rest of the division having now won consecutive league games for the first time since October.
"Everything came together for us," he enthused. "We were good defensively, created a lot of chances and kept pushing and pushing until the 90th minute. It's a rare scoreline - we've shown what we can do."