Former Villa manager Martin O'Neill allowed the 25-year-old to depart the Midlands club for Bolton in a £5m deal back in 2008.
Ahead of Saturday's match Cahill had played five times against his old club with disappointing results, drawing one, losing four and conceding 15 goals.
But the England centre-half redeemed himself at the Reebok Stadium, scoring two goals in a man-of-the-match winning performance to inspire a 3-2 Trotters victory.
little knockback
He said: "I was keen to prove a point because the last few times I've played against them I've had absolute stinkers! So the tide had to turn for me.
"In the away game last season we lost 5-1 and it was probably my worst performance as a professional. To do it at Villa Park was a big blow.
"So I really did feel I had something to prove. When you get a little knockback in your career, it gives you something to strive for.
"In the back of your mind you're always thinking 'I'll show you'.
"I know now that me leaving was the best thing. Martin O'Neill let me go and he obviously felt that was the right thing at the time. But you go on and want to prove people wrong."
