The Saddlers trailed by one-goal-to-nil at the break and were ultimately defeated by the visitors, despite a spirited performance in the second forty-five which saw four goals scored, including a Caolan Lavery brace.
Clarke, who made a few changes to his starting line-up as Zak Jules, Callum Cockerill-Mollett, and Alfie Bates made their first starts of the season, felt his side needed to defend better, particularly against the counter attack.
Speaking via the club's official website, Darrell said; "We’ve got to be better. As a group we’ve got to reorganise and not chase the game too early, we’ll always push teams back but really disappointed.
"We didn’t lock-down on the first goal, we deal with the cross so lock it down. We knew they’re a dangerous counter attacking team and we talked about so we’re thoroughly disappointed to be out of the cup.
"I thought we showed a lot of naivety out there. We’ve got to get out of the bad habit of conceding the first goal because it makes it a bit of a mountain to climb and you if you’re going to be scoring two goals you can’t be conceding three."
One positive to come from the game was striker Caolan Lavery's second-half double, the former Sheffield United forward coming off the bench to give the Saddlers some hope.
Clarke, who made a triple change shortly after his team had gone two-nil down, was pleased to see the 26-year-old get off the mark and was especially impressed with his second goal.
Darrell continued; "It’s pleasing, because he’s missed all of pre-season and not played many minutes. The last thing you want to do is killing the boy too early but he showed his quality, his second goal was a great finish."