The Magpies' youngsters held their own in the first-half of the last-16 clash before conceding two early goals after the break from identical corner kicks - with Kelland Watts' own goal and Charlie Wyke's header giving the League One side a clear advantage.

Chris Maguire and Benjamin Kimpioka sealed the win for the Black Cats with late strikes, as the Magpies were unable to claim their fourth away win in this year's competition after topping Group G with three victories on the road.

Undoubtedly, Walters was left frustrated with the final outcome and the teenage right-back felt the scoreline was not justified after the Magpies' solid first-half performance, where United's youngsters kept their senior rivals at bay whilst creating key attacking opportunities of their own.

"I don't think we deserved to lose in that manner," Walters told nufc.co.uk. "We conceded twice from two sloppy set plays at the start of the second half and, from there, we dropped our heads a little bit.

"I think it was harsh to lose by four goals considering how the game looked. Sunderland did create a few chances but, in fairness, it wasn't like they had a lot of attempts on goal. Going into half-time level, there was a belief that we could get a result.

"With such a big crowd watching, there were nerves to begin with but we were able to calm down after getting the first 45 minutes under our belt. Sadly, we switched off in the second half and conceding the two early goals cost us.

"I don't think that many people would have expected us to get this far (in the tournament) and to play Sunderland was an added bonus. Each and every one of us have given our all and we just came up short in the end."

Newcastle's attention now focuses towards reaching the play-offs in Premier League 2's second tier, with the under-23s one point adrift of Aston Villa who currently occupy the final qualification spot in the division.

And, after playing in front of over 16,000 spectators, the 18-year-old believes the occasion at the Stadium of Light will be useful for the young squad in their bid for a top-five finish.

"It was a big learning experience," Walters added. "It was the first time most of us have played in front of a crowd like that, especially in a derby. The fans sung from the first minute till the last and even when we were clapping them after the game had finished, they continued singing which was a great feeling.

"The tempo was much quicker for us and we can take a lot from the game to keep pushing on in the season. We still have a lot of matches to play and we are still aiming for promotion, so we have that to look forward to and must keep working hard in training to get into the play-offs and try to go up."