Charlie Palmer felt his side missed out on a golden opportunity to progress into the next round of the FA Vase at the first time of asking.
Evan Garnett’s late goal secured a 1-1 draw and a Tuesday night replay at Kings Lynn.
But Palmer felt it was a missed chance and that Belper could have won had they shown improved quality in the final third.
“We went in at half-time 1-0 down, but looking at the first half performance we did not deserve to be losing,” he said.
“It is about me installing the belief in the players and making them recognise that if they improve the quality in the final third, they will score a goal, like we did in the second half.
“We showed them that we can play football and cause them problems, but the thing that impressed me the most was how much tighter we looked at the back.
“We put in a good shift, we played football in some good areas, the result was probably fair but I feel we could have gone onto win the game. As I keep saying if we improve our quality in the final third we will be able to kill teams off.”
With several players cup tied, including captain Eric Graves and new signings Alex Steadman and Tyrell Shannon-Williams, some of the Nailers younger players had an opportunity to show what they are capable of.
Isaac Minott came off the bench to set up Evan Garnett’s equaliser and caused the Kings Lynn defence some real problems.
And Palmer is eager to see his youngsters build on their experience and develop their game.
Palmer added: “We had key players missing, we had a young squad and a lot of new players coming into the team.
“I have been watching the under 21 side, there are some good players coming through. I was in there position at Watford as a youngster, I am a great believer in if they are good enough then it is important to get them involved in the first team so they know what it takes to make it at this level.
“If they are patient and keep working hard the opportunities will come for them.
“All the players I am bringing into this club are lads who are young, and hungry to achieve success and go on to play at a higher level.”
“We will go down together on Tuesday night on the coach, we will prepare and set up properly and give a good account of ourselves.”
“Isaac Minnott has to be patient, it is a step up for him at this level and he still has lot of learning to do and what areas of his game he needs to work on. He will always provide opportunities for other players because he is a handful.
“Evan (Garnett) likes playing alongside him because he can take the burden off of him. That showed today when Isaac slipped him in and Evan took the goal very well.
“Like I have said before, Evan (Garnett) looks a very good player, he just needs to recognise he can cause defenders problems in and around the 18-yard box like he has done today and he took his goal very well.”
Visit www.belpernews.co.uk for full reaction from Tuesday night’s FA Vase replay.