Walsall, winners in last week's League fixture at Northampton, were unable to gain a second successive win and they will be the happier of the two to get a second bite at the cherry. Northampton showed far more urgency in the Cup game and probably deserved to go through at the first attempt, given their first-half performance.
"Our aim will be to be in the draw for the third round, that is the main thing," said Walsall boss Richard Money.
"Northampton made a real cup tie of it and if I am honest they edged it. I would like to have won it at the first attempt, but I would rather have a replay than go out."
Cobblers boss Stuart Gray felt his side showed much more appetite than last week but was disappointed not to have won it.
"We dominated the first half after going behind but the second half was scrappy and a few players were too keen to make up for last week's performance," said Gray.
"But the most important thing was that I got a good response from the players today. Although I was disappointed with our final pass in the attacking part of the pitch in the second half, I still felt we might get a chance to win it."
Mooney shot Walsall into a fifth minute lead, firing home after latching on to Mark Bradley's pass.
But top-scorer Kirk equalised in the eighth minute when he forced the ball home from close range after Poul Hubertz flicked the ball on from Andy Holt's cross.
Kirk twice went close before the break, but it took a superb save from Mark Bunn to keep out Darren Wrack's effort which came back off the upright.
Hubertz went close in the second half, Clayton Ince saving his overhead kick, but substitute Paul Hall missed the best chance of the half for Walsall, shooting wide after bursting into the box.