Valencia was in hospital on Wednesday morning having an operation to reset his ankle after he suffered an horrific injury during Tuesday night's Champions League draw with Rangers at Old Trafford.
Sir Alex Ferguson has already admitted he does not expect Valencia to be available for the remainder of the season and likened the injury to that which Alan Smith suffered in similarly freakish circumstances against Liverpool in 2006.
Arguably Smith has not been the same player since. But, as he came to terms with watching Valencia being carried off on a stretcher wearing an oxygen mask to ease the pain, the gruesome sight so bad Sky did not show a replay the incident itself, Fletcher is holding out more hope for the Ecuador star.
"It looked really bad," he said.
"Hopefully the scans show it is not as bad as we fear.
"After arriving from Wigan he had a great first season and was looking to push on this year. That is why the injury is a real blow.
"He has only just got back from the injury he suffered at the end of last season too.
"He is a strong character and a good lad. He has real determination and works hard. He will be back I am sure.
"He will have a long future at Manchester United."
Aside from the injury itself and Valencia's recovery time, it leaves Ferguson with a problem so soon after the transfer window closed.
With games beginning to pile up, starting with Sunday's clash against Liverpool, United are left with only three orthodox wingers, one of whom is the largely untested Gabriel Obertan and another, Ryan Giggs, who cannot be expected to feature in every game just two months short of his 37th birthday.
Park Ji-sung, Javier Hernandez and even Fletcher himself are capable of operating in that area but are not natural wide-men, with so much now resting on Nani if United are to keep pace with Premier League title favourites Chelsea, having already fallen four points off the pace.
A bit of work is required in Europe now after last night's disappointing result, with Fletcher joining his manager in believing the 10 changes, which admittedly did see Ferguson introduce eight full internationals, including Wayne Rooney and Rio Ferdinand, played no part in the result.
"There were not too many changes," said the Scotland skipper.
"We have a big squad and everyone has a lot of ability.
"It is difficult for the players coming in because they don't have that match sharpness.
"But training is intense and everyone is good enough to play in this team. The manager felt things needed freshening up and the team was good enough to win the match. I agree."