The midfielder gave a timely reminder of the quality he still possesses in the 5-0 UEFA Champions League win in Germany on Wednesday as he prepares to turn 40 on Friday.
Giggs had a hand in two of United's goals as the Premier League champions eased into the last 16 of the competition.
Moyes, who promoted Giggs to player-coach following his close-season arrival at Old Trafford, said: "He's an unbelievable footballer and is even getting better. His vision, his pass for Nani's last goal, you wouldn't say he needed to come off because of his fitness.
"Some people have mentioned his age , but you can't mention anything about his footballing ability.
"He's a wonderful footballer and I’m lucky to be working with him.
"I got asked the question the other day about how long he'll carry on and the situation with Ryan is that you keep playing.
"He'll tell us when he thinks he's had enough, but he keeps training, he keeps playing and his performances have been excellent."
