Visitors Darlington took the lead via Omar Holness in the first-half and looked to be heading for the Second Round until Caolan Lavery (86') and Alfie Bates (89') had put the Saddlers ahead before Jarrett Reeves netted deep into second-half stoppage time.
Clarke, who had seen his side slip to six successive defeats heading into the clash, admitted that he started the game with the wrong set up before making a double change midway through the first-half.
The Mansfield-born boss went on to criticise his team as they went on fight back from being a goal down to go a goal ahead before succumbing to a late strike which takes the time to an as-yet-to-be scheduled replay.
The Mansfield-born boss went on to criticise his team as they went on fight back from being a goal down to go a goal ahead before succumbing to a late strike which takes the time to an as-yet-to-be scheduled replay.