The manager laughed off Martin Allen’s pre match suggestion that his National League South were the favourites.
But a valiant display in Derbyshire means they get an opportunity to continue their journey after their 1-1 draw.
Brennan said: “We were excellent and the players did us proud.
“Despite what was said we weren’t the favourites and we still aren’t. Chesterfield are a huge club and it’s a Football League set-up, make no mistake about that.
“We had so much belief in what we were doing and played with no fear.
“Now it’s about trying to finish the job back at ours - that’s the challenge now.
“If we show the character I know we have then we have a chance. It’s really exciting.”