Cahill scored one and created another in stoppage time to rescue an unlikely point.
He told Sky Sports 2: "To be honest it's quite unreal but I think if we look at the chances we gave away and the chances we missed it's probably a fair result in the end.
"It was a tough game, really difficult. It just shows the fight. We've tried and tried the last couple of games and it hasn't happened. Today it was a great result."
Goalkeeper Tim Howard pulled off a string of stunning saves against his former club and was delighted with the fighting spirit showed by his team.
"The first half we dominated and we should have went in 1-0. Obviously they got the goal and in the second half they were powerful and went over the top of us.
"But we had spirit and we had fight and we got the point which was important."