Giggs, who turns 40 tomorrow, impressed with a fine display against Bayer Leverkusen in a 5-0 win last night.
Rooney said: "I've run out of things to say about Ryan.
"Actually, during the game, the Bayer centre-half was asking how he is still playing at that age.
"I certainly won't be playing at that age, that's for sure. His composure on the ball is great."
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