The Blues notched 14 goals from just two games in front of their own fans in December, but have lost both their matches played at home since the turn of the year.
A surprise 1-0 defeat against QPR was followed up by Wednesday night's 2-0 reverse to Swansea, and the former Bolton man is at a loss to explain what has changed.
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“I don’t know [what’s happened] with our home form,” Cahill told reporters.
“Normally, we are unbelievably hard to beat at Stamford Bridge and we have been getting results. We just have to be consistent in what we are doing.
“Sometimes, we are playing fantastic stuff like you saw against Southampton and Everton but then we chuck it away against QPR and now Swansea.”
Despite their home form, Rafa Benitez’s men have been in fine form on the road winning six of their last seven games away from Stamford Bridge and travel to Stoke on Saturday.