Mikel Merino (Arsenal and Spain)

The Arsenal midfielder has been a steady presence for Spain, but a fractured foot has kept him on the sidelines since February. Spain’s medical staff are wary of a premature return.

Wataru Endo (Liverpool and Japan)

Japan captain Endo is coping with a double setback involving his knee and ankle since sustaining the injury that left him in need of surgery during February’s match against Sunderland. He is set to miss the rest of Liverpool’s season and his absence for Japan would leave a big gap in terms of midfield leadership and experience.

Arda Guler (Real Madrid and Turkey)

A hamstring injury has brought Guler’s domestic season to an end. Although he might recover in time for the World Cup, concerns remain over his sharpness and readiness with limited time to regain match fitness.

Estevao Willian (Chelsea and Brazil)

The Chelsea teenage forward is recovering from a hamstring tear and will not feature again for the Blues this season. Brazil remain hopeful, but his lack of recent football makes selection uncertain. The final decision is likely to hinge on his progress in the coming weeks.

Xavi Simons (Tottenham Hotspur and Netherlands)

The Dutch playmaker looked in distress after he suffered a knee injury at Wolves. He later said the issue had brought his Premier League season to an end and would rule him out of the World Cup.