According to various reports, Manchester United are eyeing three West Ham players ahead of the January transfer window.

The transfer window re-opens in just over a month and under-performing Man United are seeking reinforcements.

The Mirror reports that Jose Mourinho has his eyes on Marko Arnautovic, as he tries to add fire power up front.

The Metro adds that Declan Rice is being watched by the Red Devils. And The Daily Mail claims Mourinho wants Issa Diop to solve his problems at the back.

But can West Ham afford to lose any of these players in January? We take a closer look…

Marko Arnautovic

Marko Arnautovic is the key man for West Ham up front. (Photo by Justin Setterfield/Getty Images)

Given Arnautovic’s fine form, it is no surprise to see him attracting attention.

The Austria international has been reborn at West Ham, featuring in a centre-forward role.

The 29-year-old has scored five goals in 11 games for West Ham this season, adding to last season’s tally of 11 in 31.

Arnautovic is a maverick talent and he is West Ham’s talisman; his presence on the pitch can lift his team-mates.

With pace, power and an eye for goal, Arnautovic is the complete striker.

But he will enter his 30s by the end of the season and if this report is accurate, Man United will offer more than £50m for his services.

Taking his age and his chronic knee injury into consideration, this is a bid that West Ham must take seriously.

Arnautovic would be hard to replace but that money could be reinvested wisely.

Issa Diop

Issa Diop joined West Ham from Toulouse in the summer. (Photo by Arfa Griffiths/West Ham United via Getty Images)

Diop only joined West Ham this summer but he has been in fine form at the back.

The 21-year-old plays with maturity beyond his years and he is the full package.

Offering pace, strength, commitment and the ability to read the game well, the France under-21 man has a big future ahead of him.

Losing Diop would significantly weaken West Ham’s defence and the Hammers must keep hold of him in January because his value will continue to rocket if he stays.

Declan Rice

At 19, Declan Rice is already a West Ham regular. (Photo by James Griffiths/West Ham United via Getty Images)

Losing Rice would be the most devastating out of the three, perhaps because many West Ham fans feel this is avoidable.

The 19-year-old is keen to stay but he is not being offered a contract which reflects his importance to the first-team.

Rice is already one of West Ham’s standout performers and he has the potential to reach the very top of the game, either as a holding midfielder or as a centre-half.

The teenager, who is agonising between representing Republic of Ireland and England, sits in front of the back four and breaks up play expertly.

Rice can be the future West Ham captain but losing him to Man United in January would seriously deflate the fans.