The Chelsea defender was part of the side that thrashed Villa 8-0 at Stamford Bridge in December but he is not expecting such an easy ride on Saturday.
"We played them at home and we got a convincing result there," said Cahill, who began his career at Villa before joining Bolton in 2008.
"This time around it will be a different team we face. They're playing some good football and attacking-wise they look very strong.
"It's going to be tough, but I'm looking forward to going back to my old club and looking forward to the game.
"We've got three games that could determine our season. We have to keep pushing."
Chelsea interim boss Rafael Benitez agreed with Cahill's assessment, adding: "It doesn't matter what happened in the game at Stamford Bridge.
"The main thing is they want to win, they need to win. They're doing well. It will be tough because they're desperate to win and stay in the league."