Jose Mourinho and Manchester United still have a lot of work to do to bring the Old Trafford side back to the glory days that supporters became accustomed to under Sir Alex Ferguson.

Progress was slow initially, United struggling for form and looking like they may be stuck in their slump for yet another season. But things have been going better recent and Mourinho's side are now well placed to push on and secure a Champions League place.

That will require a big January transfer window though, with some of United's squad members not showing the form required to be a part of one of England's best sides.

What changes are required and where can Mourinho make the biggest improvements? Fortunately for United, the winter window officially opens as soon as Big Ben strikes midnight on New Year's Eve.

Here are THREE glaring issues that the Old Trafford club must solve in January to continue Mourinho's revolution...

High earners not performing

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Manchester United's Marouane Fellaini looks dejected after conceding a penalty for a foul on Everton's Idrissa Gueye 
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Marouane Fellaini is just one of a number of United players whose time is likely up at Old Trafford. One of Mourinho's main priorities in January will be finding a home for these high-earners so that he can use the resources available to him to really push on with his squad overhaul.

Moving players on allows room for fresh bodies who have no baggage at the club and are willing to buy into Mourinho's style from the off.

Morgan Schneiderlin, Memphis Depay and arguably Anthony Martial could all be on this list. Can the club do good business with these high-earning assets?

No back-up for Ibrahimovic

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Manchester United's Zlatan Ibrahimovic celebrates scoring their second goal  
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Zlatan Ibrahimovic is having an absolutely exceptional season but should he pick up a knock, a more serious injury or even lose form, United have no viable replacement that can step up to his performance levels this year.

Signing a quality striker would not only give cover but provide competition and offer different tactical options for Mourinho.

There's also an obvious negative with Ibrahimovic - his age. He's not a long-term solution in the position and United need to start working now to bring in a striker who can play at Old Trafford for years to come.

No prime partner for Pogba

If United can sign another quality midfielder to compliment Paul Pogba, they'd arguably have the strongest first choice midfield in the world.

Paul Pogba has shown he can be worth every bit of the world record transfer fee that brought him back to Manchester and is relishing his role as United's talismanic force.

Herrera and Carrick offer good options, but not quite equal to the class that Pogba has. With Carrick getting towards the end of his career at the top level, January is a perfect time to push the boat out and sign a replacement who can form a partnership with Pogba.