Jamie Carragher has suggested that Wayne Rooney is at the level of a player five years his senior due to "miles on the clock".
The 30-year-old has made 580 competitive appearances at Everton and Manchester United in a senior career spanning 14 seasons, in addition to picking up 109 caps for his country.
Rooney has been criticised for his form for Louis van Gaal's side this season, although his late stunner against Swansea City on Saturday helped United to their first win in eight.
"If you are going to write Wayne Rooney off or say he is back, you can't say he is back because of one moment in a game and you cannot write him off because of maybe two or three bad games," Carragher told Sky Sports News. "We have said before he was playing at 16, so in reality terms he's maybe like a 33 or 34-year-old player. People talk about age, it's miles on the clock and it's games played. He must have played nearly 600 [club] games as a centre forward, which is maybe not the same as playing in the position I did.
"I just think that battering from centre backs and the pressure that is on him, mentally as well, to play from that age of 16 - I think we are looking at a player who is getting to the stage of his career where I don't think he will be playing at the top level at 34-35. I just think he's been playing so long now that maybe it's 30 on his birth certificate but in terms of games played he's a 35-year-old player.
"I think for Rooney to answer his critics or show he is still the man to play centre forward for Manchester United he maybe needs a run of 10 games — scoring maybe seven or eight goals."
The winner against the Swans moved Rooney up to second on United's all-time scoring chart, with his 238 goals 11 shy of Sir Bobby Charlton's record.