Fixing Manchester United in the January transfer window

United's interim manager has had the perfect start to his interim at Old Trafford with a 1-5 drubbing of Cardiff City away from home, yet the cauldron of uncertainty that has been left behind by Jose Mourinho still threatens to boil over Ole Gunner Solskjaer's plans for returning his former side to the Top-four.

Party to this has been the inadequacies present in the squad from back to front. A disillusioned Romelu Lukaku, a back-line which is yet to go unchanged for over a week of Premier League football and an ageing Nemanja Matic who clearly doesn't have the legs to break opposition attacks.

Reports indicate that the Solskjaer will have around $50 million to spend in the transfer market. Let's take a look at what he might be looking at in the market.

1. Kalidou Koulibaly

Koulibaly has emerged as one of the best in the world
Koulibaly has emerged as one of the best in the world

The Red Devils have let in 30 goals in just 18 Premier League matches. To put that in context United concede around every 50 minutes of football pitch action. That is a damning statistic for a side aspiring to dominate World Football.

The solution it seems lies with Napoli currently. Senegalese defender Kalidou Koulibaly has earned rave reviews during his time in Italy. Big, strong and deceptively quick, the 6'2 centre-back is comfortable in bringing the ball out of defence. something United have lacked since Rio Ferdinand's departure.

He has a $103 million release clause which if activated would make him the World's most costliest defender but having witnessed Virgil Van Dijk's impact on Liverpool, the record they would be beating if they go after Koulibaly, the United hierarchy need to act quick before PSG or Real Madrid swoop in.

2. Douglas Costa

Costa has lost his place in Juve's starting line-up
Costa has lost his place in Juve's starting line-up

The left-flank of United's midfield has the likes of Anthony Martial and Marcus Rashford to fill in, a devastating proposition for defenders but it's the right side where they are found wanting. Having experimented with Juan Mata and Jesse Lingard this season, Solskjaer is clearly in the market for a right-winger.

This where the prospect of Douglas Costa gets interesting, the Brazilian is an old fashioned wing-player who likes to hug the touch line and deliver crosses, beating his marker for pace. While Lingard is more of roaming presence, Costa would fill in a huge void in United's attack.

Currently at Juventus, the Brazilian has to compete with the likes of Dybala and Ronaldo for a place in the starting line-up, United can offer him a way out.

3. Adrien Rabiot

- Rabiot is available on a free next summer
- Rabiot is available on a free next summer

Having fallen out with PSG boss Thomas Tuchel, Adrien Rabiot has declined to sign a new contract at PSG. Which means that the Frenchman will be available on free next-summer. PSG will be desperate to cash on the midfielder in January and that's where United could make their play.

At 6'4 Rabiot is a hulking presence in centre-midfield and can dictate play form a deep-lying position. Which will in-turn free Paul Pogba to carry on with his attacking work. Only 23, Rabiot will be an absolute prudent investment for Ed Woodward and co. having considerable Champions League appearances as well as the legs to replace Nemanja Matic.

To get their hands on Rabiot, United would have to beat competition from the likes of Barcelona, Liverpool and Tottenham.

4. Mason Greenwood

Greenwood has impressed for the United reserves
Greenwood has impressed for the United reserves

The return of United's old guard in the form of Ole Gunner Solskjaer means that we could see a revival of youth players in the United setup. At the top of the pile is 17 year old Mason Greenwood. The young forward recently netted a hat-trick to knock-out Chelsea in the FA Youth Cup.

And if reports are to be believed, Solskjaer is already in talks to promote the youngster to the match-day squad following the struggles of Romelu Lukaku. Greenwood would be a welcome addition for the supporters who have been left scratching their head over the $75 million United paid for Lukaku.

Their FA Cup encounter against reading could see the striker included in the line-up after what has been a fantastic year for him.