West Ham have been dealt a blow after it emerged that Jack Wilshere will be out for up to six weeks following surgery on an ankle injury.

It had been hoped that Wilshere would not require an operation after he sustained a sprained ankle in training last week. Yet the problem was serious enough to keep the midfielder out of his club’s victory at Everton on Sunday and he is set for an extended spell on the sidelines after having a minor procedure on Monday.

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The 26-year-old’s latest setback is a blow for Manuel Pellegrini, who pushed for Wilshere to be given a three-year deal in the summer. West Ham’s board only wanted to give the former Arsenal player a one-year contract because of concerns over his injury record, only to give in to Pellegrini’s demands.

The move for Wilshere, who left Arsenal on a free transfer after discovering he would not be a regular starter, was seen as a risk by senior figures at the London Stadium club. Yet Pellegrini identified him as a key target after replacing David Moyes as manager at the end of last season. The Chilean had repeatedly insisted that he was not worried about Wilshere’s fitness problems and revealed that West Ham had devised a personalised training regime for the England midfielder after signing him in July.

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Wilshere, who endured ankle problems during his time at Arsenal, has struggled to find his best form this season and was substituted during the 1-0 home defeat against Wolves this month.

Debate has swirled over his place in the side, too, though Pellegrini has remained supportive, even suggesting Wilshere is good enough to flourish in the kind of deep role that Andrea Pirlo played for Juventus.

But after losing their opening four league fixtures West Ham travelled to Goodison Park without Wilshere and produced an improved performance to move off the foot of the Premier League table. Pellegrini’s side were more robust with a midfield trio of Mark Noble, Pedro Obiang and Declan Rice.

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West Ham’s head of medical Richard Collinge confirmed the operation had been successful. In a statement on the club’s website, Collinge said: “Jack underwent successful surgery in London on Monday morning. The surgeon was happy with the procedure and all went as planned.

“We envisage he will only need a relatively short period of rest and will then start his rehabilitation. Jack is focused and determined to get back training as soon as possible.”

On a brighter note, West Ham remain hopeful that the knee injury that forced off Marko Arnautovic at Everton will not prove serious enough to keep the Austrian forward out of the home game against Chelsea on Sunday.