The Chelsea captain has started three of the last six matches after missing the festive period with a knee complaint.
"He's a massive character and leader for us," Cahill said. "He's been struggling with his injury a bit, but has come back again.
"It's just great to have everyone back fit. You don't want people sitting in the treatment room if you can help.
"To have most of the lads back out there with us now is a healthy situation."