The Bulgarian international is the highest profile name under threat of being axed by Sir Alex Ferguson - but is one of a host of underperformers on the verge of being shown the door.
Also on that list are Nemanja Vidic, Nani, Michael Owen and Anderson, who have all struggled with either fitness or form this season.
Ferguson may yet spend in the January transfer window, with a proven goal-scorer and a creative midfielder his priorities - but his major rebuilding will be done in the summer, when a number of names are expected to depart.
Berbatov remains his biggest dilemma, with the United manager never happy to admit defeat with a high-profile signing - especially one so expensive.
At £30.75m, the former Tottenham striker is still a club record signing, but has rarely justified such a hefty price tag.
After struggling to settle in his first season at Old Trafford, Ferguson hoped the departure of Cristiano Ronaldo would inspire the best out of Berbatov, saying last summer: "We were a bit unfair to him last season, but we know how to use him this season and he won't change from that."
There has been no evidence of that with Berbatov managing only six goals so far this season.
For all his public support of Berbatov, Ferguson made no secret of his desire to sign a world-class goal-scorer with his failed bid to land Karim Benzema last summer.
The Frenchman - who opted to leave Lyon for Real Madrid instead - remains on United's wanted list, either this month or at the end of the season.
Other strikers being monitored are Wolfsburg's Edin Dzeko, Valencia's David Silva and Porto's Brazilian international Hulk.
Ferguson's determination for more firepower - despite having the potential of Danny Welbeck and Federico Macheda in his squad - also places doubts over Owen's future. The former Liverpool man's dream move to United has turned out to be anything but, with Ferguson clearly not convinced by his form.
Owen has only been used sparingly this season - and despite a record of seven goals in nine starts, is still to be given a consistent run in the team. Even if United don't look to sell in the summer, the 30-year-old could seek a move himself to get regular first-team football.
Vidic's days also increasingly look numbered.
It is an open secret that he wants to play in Spain - and with Barcelona and Real both waiting in the wings, now would be the time to cash in on the Serbian.
Despite being a popular figure at Old Trafford and one of Ferguson's most astute buys at £7m four years ago, there is little argument that his powers have waned over the past 12 months.
Vidic has this week denied a rift with his manager, following his late withdrawal from the FA Cup defeat to Leeds, saying: "Everybody in the club knows that I have a marvellous understanding with my coach Ferguson. I am not unhappy at Old Trafford. I am just injured and I hope that I will be able to play as soon as possible."
Still, United could expect to pick up in excess of £20m if they decided to cash in, which Ferguson would struggle to justify turning down.
Making such sizeable profits on Nani or Anderson would not be so easy.
The pair were signed for over £30m between them in 2007 and have struggled to live up to the hype that surrounded them upon their arrival.
Nani has been particularly disappointing, prompting Ferguson to sign first Zoran Tosic and then Gabriel Obertan to fill an increasingly problem position on the left of midfield.
The Portuguese international's outburst earlier this season, claiming he'd lost confidence due to the manager's chopping and changing of the team, was seen as the last straw.
Still United will need someone to come in with a reason- able offer for the frustrating winger or else accept a big financial hit, having paid Sporting Lisbon in the region of £16m for his services.
Anderson will be given more of a chance to prove he is United quality - but has shown rare signs of living up to predictions that he is the natural successor to Paul Scholes or that he will one day be the best player in the world, as scouts told Ferguson before he splashed out around £18m for the former Porto midfielder.
With United only two points behind leaders Chelsea at the top of the Premier League and through to the knockout stages of the Champions League, Ferguson is hardly at the point of panic. But he knows his side are where they are in spite of their underperformers rather than because of them.
And time is running out for those players to prove they still have futures at United beyond the end of the season.
Source: Manchester Evening News