Friedel is 38 but has shown no signs of his qualities diminishing since making the move from Blackburn nearly two years ago.
He produced a string of stunning saves to deny Birmingham in Sunday's derby before a late penalty from James Milner kept Villa on course for a top-four spot in the Barclays Premier League.
Downing said: "Brad made some superb saves against Birmingham but then he's been doing that all season and been important for us.
"He was quiet for a long time in the game but, when he was called upon, he made some terrific saves and that's the sign of a good goalkeeper.
"Sometimes you need a bit of your luck and your keeper to pull one or two off some top class saves and he did that for us on Sunday and has done it before.
"It's hard to believe he is approaching his 39th year because he looks after himself and he's very fit.
"As long as he does that, then he'll carry on playing and you can see in his performances that age doesn't matter."
Downing is relishing being involved in a battle for honours after being part of the Middlesbrough side relegated from the top flight 12 months ago.
He said: "We have left ourselves with a great opportunity to finish fourth and end the season on a high.
"It's been brilliant this season. I've been to a cup final and a cup semi-final and we're consistently winning games.
"It's a winning environment really. It's a big change from where I was at last April when we were struggling (at Boro). The team are playing well.
"I think we've played better than we did against Birmingham. Some games you don't play well and win and that's a sign of a top team.
"The top teams have done it for a while. We've played a lot of games in succession and that was a very good win. That's all we need to do, win the games."