The Finn, 38, has earned a new 12-month contract.
Allardyce said: "You just have to look at him. His wife Tess says he doesn't look 38 - especially when he has a shave. He's a young 38.
"He's never suffered many injuries or operations and that is always a really good sign.
"Brad Friedel is probably the catalyst for every goalkeeper if you look after yourself and use your experience.
"Your body might slow down but if your positioning is perfect you save shots.
"And if you keep yourself fit, at that age you should very rarely get caught out of position as you have all that experience behind you.
"The goalkeeper and goalscorer are the two biggest positions to fill.
"Having one at one end scoring the goals and the person at the other end saving them are the most important and he's done a great job this season."