The Saddlers dominated the first half of the contest and deservedly led at the break ahead thanks Dan Scarr's well-taken goal five minutes before half-time, the Saddlers seemed well on the way to building upon their recent victories over Nuneaton Borough and Polish-outfit Odra Opole.
But, following a string of second-half substitutions - including eight by Clarke himself - the home side went on to seize the advantage with Dutch winger Enzio Boldewijn netting a second-half brace as the Magpies went on to win in front of 1,390 fans in Nottingham.
Speaking to the Express & Star's Saddlers correspondent Joseph Masi, Darrell said; "I thought the first 60 minutes were brilliant. I thought we were really good. We were on the front foot and should have had two or three goals.
"The last 30 minutes, s***e. It was not good enough. We have got some young lads out here but they have got to learn quickly. It is as simple as that. I’m not going to gloss over the last 30 minutes.
"But the first 60 I was really pleased with what I saw. We were high energy, we forced them into errors. We have got to be more clinical, yes, we understand that.
"But a lot of the things we have been working on, the high press, worked on numerous occasions in that first 60. So I am going to focus on that at the minute."
Striker Josh Gordon and summer signing Elijah Adebayo continued to compliment each other during their spell on the field, but neither was able to take any of the opportunities that came their way, with the manager ultimately replacing the duo as he continued to take a look at the options available to him.
Clarke, who is hoping to add more players to his squad before we reach Transfer Deadline Day, went on to praise the pair but admitted that the team should've made more of their various openings as they had enough chances to put the game to bed well before Boldewijn's brace.
The gaffer continued; "We got into dangerous positions. Josh and Elijah worked really hard up there but they have got to be clinical in those key moments and at key times in games.
"We didn’t do that. We didn’t get that second or even third goal to see it off. Then there were wholesale changes after 60 minutes and we didn’t perform to the standards I expect. But for 60 minutes we were pretty dominant which is pleasing to see."