"It was strange," the youngster told MUTV. "I've not played there [left-back] for over a year now, but I thought I adapted quite well to the position and Rio and all the other players helped me out a lot, so I thought I did quite well.
"They've all got great experience and they're great players to play with. I grew up watching all of them and to play in the same team as them is great. I really enjoyed it."
Club captain Vidic, meanwhile, was suitably impressed with Keane's endeavours, admitting: "I'm glad he's had a full ninety minutes. He was confident on the ball and it's a big change from the youth academy, obviously, and I think he did really well."
Whether or not Keane is involved in the Reds' next outing, against Barcelona on Wednesday, he is merely relishing the chance to be a part of the senior squad's pre-season preparations.
"It's been good so far," he said. "We've only been here a day but we had a good time around the hotel and the game today was a great experience. It [the Barcelona game] is a great occasion for everyone and it'll just be a great game to watch, never mind play in if I get a chance. I'm looking forward to it."