Fred's arrival could spell doom for some Manchester United players

With the World Cup frenzy having finally concluded, Premier League clubs can now get back to their transfer business as they try and finalise their squads before the start of the 2018-19 season.

With the transfer window closing on 9th August this year instead of the traditional 31st of August, expect a flurry of deals being closed in the next couple of weeks.

Every English top flight club, with the exception of Tottenham, Everton and Burnley have already signed at least one player, with the most notable ones being Riyad Mahrez (Man City), Fabinho (Liverpool), Jorginho (Chelsea) and Fred (Man Utd).

United's signing of Fred in particular could signal trouble for some players at Old Trafford.

Fred in action against Roma in the Champions League

The Brazilian midfielder arrived for a sum of £52 million on the 5th of June from Ukrainian champions Shakhtar Donetsk.

He'd been linked heavily with Man City in January, as Pep Guardiola stepped up his pursuit of a central midfielder, but the deal didn't go through.

Known for his all-round abilities in midfield, Fred is equally impressive in both attack and defense, the prototype of the modern day box-to-box midfielder.

Its safe to assume that Mourinho intends to utilise him in a midfield trio with Nemanja Matic and Paul Pogba.

Matic is your typical defensive midfielder, there are few players in the Premier League more imposing than him. He adds steel to a midfield that looked dangerously fragile before his arrival, and was one of United's stand-out outfield players last season.

Pogba - World Champion!

The jury's still out on Pogba, but his performances at the World Cup proved once again that he's at his most effective when given freedom to roam the midfield. And luckily for Didier Deschamps, he had N'Golo Kante operating behind the United man to protect the French defence.

Which is probably what Mourinho will expect from Fred at United. He provides a two footed option in midfield who can provide an added layer of protection to the defence, while also providing an extra attacking outlet up front when required.

Unfortunately, this could mean that Ander Herrera will get even lesser game time than he did last season.

Since signing from Athletic Bilbao in 2014, Herrera quickly established himself as a fan favourite at Old Trafford with his energetic and passionate displays in midfield.

Herrera scored the decisive goal in the FA Cup semifinal against Spurs

It was during Mourinho's first season that he truly established himself as a crucial squad member, being deployed regularly in midfield with Pogba and Carrick.

But last season, his playing time was cut short again following the signing of Matic from Chelsea.

Fred's playing style is too similar to Herrera's, and Mourinho is probably going to favour his new signing when it comes down to a choice between the two.

Herrera will turn 29 on the 14th of August and will have to fight tooth and nail to be in Jose's plans for next season.

Scott McTominay is another option in midfield for the Portuguese boss. He endeared himself to the Old Trafford faithful last season after an injury to Pogba gave him a run in the first team.

The United academy graduate recently made his debut for Scotland

His simple and accurate passing was exactly what United needed in the absence of their midfield powerhouse. Fred's arrival is bound to have an impact on his playing time as well.

But at just 21 years old, he's probably going to be sent on loan to gain more experience, and his career at the Theatre of Dreams is not over by a long shot.

For Herrera though, the clock's ticking.