South American football expert has one doubt over Radamel Falcao

BBC football expert Tim Vickery says doubts over Manchester United striker's age are unfounded, but questions could be asked over the state of his knees.

Clinical penalty box striker Radamel Falcao signed for Manchester United on transfer deadline day earlier this month and joined fellow marquee names like Angel di Maria at Old Trafford.

His addition to Louis van Gaal's roster is expected to usher in a new era at United, as the club look to find the cure to the 15-month hangover from the post Sir Alex Ferguson era.

Falcao, 28, is a peak-form forward capable of prolific goal-scoring, however, there have been question marks over the legitimacy of his age claims.

These have been countered by "school teachers" who have "confirmed he is 28", according to South American football analyst Tim Vickery.

However, Vickery does have one doubt over Falcao - and that concerns the strength of his knees.

Falcao suffered an injury to his anterior cruciate ligament in January earlier this year. “The question for me is how old are his knees? You wonder if he has paid the price for working night and day to get fit for the World Cup," said Vickery on talkSPORT.

“He suffered that serious injury at the start of the year and the line at the time was there no chance [of recovery]. He worked so hard to try to get fit, but failed, and has he paid a price for that? He didn’t start for Colombia in their friendly against Brazil this week and only came on for the last 15 minutes, which is a declaration he’s not fit.

“As long as he’s fit he will score reams of goals from the service he will get from di Maria. And let’s hope he is fit because it’s wonderful for the Premier League to have a player like that, but that question mark will exist until he gets out on the pitch and proves otherwise."

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