England and Saracens have been left with a gaping hole to fill after confirmation that Billy Vunipola will be out for four months following knee surgery. The No8 has had an operation to repair the meniscus on his right knee and now faces a race to be fit for the start of the Six Nations in February.

Vunipola was forced to pull out of the British & Irish Lions tour to New Zealand this summer with a shoulder problem. He also missed virtually the whole of last season’s Six Nations after sustaining a similar injury to the same knee.

The injury that has already kept Manu Tuilagi out this autumn is not dissimilar and the early-season attrition rate shows little sign of slackening as England gather in Oxford for this week’s training camp. Harlequins’ Jack Clifford has been called up as Vunipola’s replacement, leaving Wasps’ Nathan Hughes in pole position to wear No8 in the November internationals.

Saracens, too, will have to readjust with their South African flanker Michael Rhodes also now facing a lengthy lay-off. It is Vunipola’s absence, however, that will inevitably have the most serious impact.

“For any team to lose a player of the ability of Billy is a blow and he will be missed through the autumn for both Saracens and England,” said Mark McCall, Saracens’ director of rugby. “It’s desperately disappointing for him, considering how hard he has worked during the off-season to get back to full fitness. But Billy is a resilient character and he’ll have a strong support network around him to get him back on the field in the best possible shape. What’s now important is his recovery and we look forward to his return later this season.”

Vunipola, ironically, has been warning in recent days that the rugby authorities need to make more effort to protect players, given the game’s rising intensity. Proposals to extend the domestic season until the end of June have alarmed an increasing number of players with Vunipola, 24, declaring his body “could not handle” the repeated beatings it received.

“It’s about the toil we’re put through,” he said, suggesting a strike might yet be the players’ response. “Something is going to give. Something might happen where we follow the NFL or NBA, where they had a lockout. It comes down to how much we play. I might think I’m strong and tough but I’m not. I just got worn down.”

Another contender for an England squad place, Exeter’s Sam Simmonds, also left the field on a stretcher after a heavy collision with Hughes at Sandy Park but the Chiefs’ management say he was up and about in the dressing room after the game and are hopeful he will not be a long-term absentee.