The match finished 2-2, with Dons winning on penalties.
Lewis-Skelly and Nichols have been involved with the senior team in recent weeks and Ali told arsenal.com: “You have to be really careful because the stimulus has to be right for them and when you get that early exposure like they’ve had, it’s been brilliant and they’ll learn loads, but then when you do come into a u21s fixture, it’s how you control your mindset to go and perform at that level.
“Myles did that really well in possession and even out of possession, learning the role as a left back. I thought he was excellent.
“Josh should’ve been better on Saturday with the level he’s been playing at but his performance tonight I was really pleased with. That’s not easy to do and you need the right mindset for it and we showed that tonight.”
Andre Harriman-Annous and Nathan Butler-Oyedeji struck Arsenal's goals and Ali added: “In the second half, Josh Nichols coming on gave us some good football moments where we moved the ball from right to left and moved their structure really well. We could’ve gone on and won the game because we had more than enough opportunities in the second half.
"We didn’t take those and we’ve got to be better with the penalties at the end, but overall I’m really pleased with the lads and proud. They’ve got to keep building from that."