Page, who played alongside the midfielder for Wales, reckons the veteran has another couple of seasons in him yet.
"Ryan has taken care of himself down the years and he's seeing the benefit of that now," said the former centre-half to The Sentinel.
"I'd think he has another couple of seasons in him. That's an achievable goal, definitely, and I can see him making 1,000 appearances for United.
"What he has done is absolutely phenomenal.
"He's a year older than me and to still be playing in the Premier League is unbelievable really.
"To still have that ambition and drive is testament to what he's all about."