Collyer started the 2-1 preseason friendly defeat.
"It's really, really, really valuable," he told manutd.com.
"I think that's what everyone wants to do. Everyone wants to be able to play in the first team. So I think getting experiences like this in a stadium like this as well, it's the top level, and obviously the opposition as well today.
"So I'm taking everything step by step and hopefully I'll get many more opportunities to show what I can do."
On Casemiro as a midfield partner, Collyer continued: "It's so valuable.
"He's one of the best ever in that position, so it's great for someone like myself to learn off him, even just to watch him in training and have him next to me, always talking to me and helping me out, as well as the other lads as well. He's a real leader in the team."
He added: "It was a tough game, but I thought we did well as a team.
"We did some good things, and some things to improve, but I thought we had the right attitude and we tried to do the best with what the manager was telling us to do.
"Was I pleased with how I played? Yeah, I thought I had an okay game. I thought there was a lot of things I could have done better, but it's great to experience a game like today and I can take it into the next game, and even into training tomorrow."