Manchester United reportedly fear Zlatan Ibrahimovic might never fully recover from the injury that kept him out of action for seven months.
Having been ruled out since April after he ruptured his knee ligaments against Anderlecht in the quarter finals of the Europa League, the Swede returned to action in United's 4-1 win against Newcastle United in November.
The 36-year-old has since come on as a substitute against Brighton and Hove Albion, Watford, Basel and Manchester City but he is yet to start a game following his return from injury and has played just a combined 73 minutes of football across five games.
Unsurprisingly, the Swede, who scored 28 goals from 46 appearances in all competitions in his first season at the club last term, has looked far from match fit since returning to action.
According to the Sun, United's medical team who has closely monitored the striker's rehabilitation every step of the way, fear Ibrahimovic might never completely recover from the injury, which would have been career threatening even for players much younger than him.
"If people knew the real injury they would be in shock that I was even playing," Ibrahimovic said last month. "It was more than the knee but I will keep it personal."
The former Barcelona and Paris Saint Germain striker, however, could be given more minutes in the coming weeks, after Jose Mourinho hinted a degree of squad rotation will be needed to cope with the traditionally congested festive schedule.
Starting from Sunday (17 December), United face back-to-back trips to West Bromwich Albion and Leicester City in the Premier League, with a visit to Bristol City for the fourth round of the Carabao Cup sandwiched in between.
With Romelu Lukaku struggling for form despite scoring the winner against Bournemouth on Wednesday [13 December], a fit-again Ibrahimovic would provide Mourinho with a very reliable alternative up-front.
The Portuguese, however, is aware the 36-year-old could need more time to recover and has already had to withdraw him from the squad twice to allow the former Sweden captain to train in the gym to try and build up the strength around the knee.
Mourinho is a keen admirer of Ibrahimovic and last month it emerged United were ready to open negotiations over a new deal with the Swede, which could keep him at Old Trafford for a further 12 months.
According to reports, the 36-year-old will be offered a 12-month extension in January, before making the expected leap across the Atlantic and end his career in Major League Soccer.