The 23-year-old, plucked from non-league Havant & Waterlooville in the summer, came on at half-time against Burton on Saturday and helped the Dons come from a goal down to win 3-1.
Arthur has yet to start a league match but Ardley plans to "unleash" him when the time is right.
He said: "I am pretty sure that there would have been a few raised eyebrows among our supporters when we signed him.
"He was our first signing of the summer and people may have been wondering where we were going with it as he came from two leagues below.
"But they can see a player with so much potential. I am still looking after him though and developing him. The staff are working hard on him and there will come a time when we decide to unleash him."