Cahill, 27, was outstanding at Norwich City and Benitez admits he is delighted with his progress.
He said: "If we continue working hard in training and Cahill continues working hard and is keen to learn, I think he will improve even more.
"How much, we will see. He's good in the air, he can play the ball, he's quick, so he just has to adjust some movements and he will be even better.
"He has to learn from everyone. JT has experience but Branislav Ivanovic is also very strong.
"Cahill is learning from everyone and I hope he can improve a little bit every game.
"For us, it's about trying to do all the things we want to do, being comfortable in possession, and he is doing this.
"Since I arrived we have been working with different defenders.
"Obviously, JT was not here and we were using Cahill, Ivanovic and David Luiz and all of them were doing a great job.
"We have some clean sheets and are stronger in defence. Still you can concede, just a corner or free-kick can make a difference. But the team is stronger in defence and we have the balance because we can attack."