Cass, who was also an unused substitute for United's Premier League win against Fulham on the final day of last season, was named on the bench along with youngsters Elias Sørensen and Tom Allan as the Magpies were held to 1-1 draw against the League One outfit at Spotland.
Although the opportunity of making his debut for his boyhood club was unfulfilled, the 19-year-old believed the occasion itself was beneficial for the inexperienced defender and is aiming to grasp more chances at senior level.
"It was a great experience to be involved with the first team," Cass told nufc.co.uk. "It's completely different to under-23 football as you get more information before the game and at half-time and things like that. I took all that in and hopefully I can use it in future games.
"It was a little bit different to when I was on the bench against Fulham due to some of the ways that the coaches approach it and how they talk to the players. I liked to be a part of that and see what is different.
"Steve Harper mentioned the day before that we (Elias and Tom) would probably be travelling with the lot and after I trained, I went home and then got a text on Thursday night saying that I'd be travelling the next day with the squad.
"I was training for two days before the game with the first team which was really good. Training with the senior players helps build up your confidence and, hopefully, I can get a lot more opportunities like that.
"It is a bit strange because, even though I've grown up playing with the likes of Matty and Sean (Longstaff), there were players who have signed for millions of pounds, who I've watched on the telly and you're then training with them.
"I can take a lot from that occasion because the coaches put us in there for a reason and haven't just picked us out from a hat. We can build confidence from the experience and potentially strive for more up there."
Cass (far left) in the warm-up ahead of Newcastle's Emirates FA Cup clash away at Rochdale
Newcastle's second-string are back in Premier League 2 action on Friday when they face their Manchester United counterparts at Leigh Sports Village (kick-off 7pm GMT).
The Red Devils sit in second place of division two but, after the young Magpies' impressive 3-0 win against Fulham, Cass believes the squad can build on the positive result as they bid to reach the play-offs for a second consecutive season.
"Our spirits have definitely lifted after the (Fulham) game," Cass added. "We've kept our first clean sheet for a while and scored a lot of goals so we'll be heading into the Man United game with great confidence.
"Stopping goals has been a priority for us and it is always going to give you a great chance of winning games so we'll be looking to do that against Man United.
"I think there's a point to prove after the last game against them (a 4-0 defeat at St. James' Park in August). We'll go there hoping to get a result and try to frustrate them in the first 20-25 minutes by keeping a tight shape and staying in the game as long enough to try and win it.
"Last season against Man United, I tore an ATFL in my ankle which kept me out for three months. It wasn't the best for me and although I'll be going there with some bad memories, hopefully I can last the full 90 minutes this time and a positive result would mean a lot to me.
"Winning at Man United last season (a 4-1 away triumph) put a lot of confidence into the boys as we pushed on from there and we'll look to use that as a stepping stone to keep going this season.
"We've done alright in parts of the first half of the season but we're aiming to do a lot better. For the second half, we're pushing for a lot more, especially the play-offs. If we can get two or three games together, then we can certainly push higher in the league table in order to reach those spots."
