Vunipola only returned from broken arm at weekend, but has been ruled out of Saturday’s Aviva Premiership game against Gloucester

Billy Vunipola has suffered yet another injury setback that casts doubt over his involvement in England’s summer tour to South Africa.

Vunipola withdrew from Saracens training on Wednesday afternoon because of a tight hamstring that has ruled him out of at least Saturday’s Aviva Premiership clash with Gloucester and he is being assessed to discover the extent of the damage.

The number eight has played only 249 minutes over the past year due to shoulder, knee and arm problems and his last international appearance was against Ireland in March 2017.

“Nothing happened, he just felt some tightness and awareness of that tightness. The hamstring hasn’t been pulled,” Saracens director of rugby Mark McCall said.

“He would like to play against Gloucester but we won’t play him if we think he will pull his hamstring in the game.”

Vunipola made his comeback from the fractured arm incurred on Champions Cup duty in January as a second-half replacement against London Irish on Sunday and made an instant impact with a succession of effective carries.

The 25-year-old entered the match with minor concern over his hamstring, however, and the discomfort has resurfaced in training.

Saracens will hope he recovers in time for their Premiership semi-final against Wasps or Newcastle on May 19, but given his injury record there is concern over his long-term fitness that could have implications for England.

Eddie Jones names his squad for the three-Test series against the Springboks next Thursday and he will be anxiously waiting for a medical update on his most destructive ball carrier.

“It was mature of him not to try to plough on in training. If we have to scan it we will. That’s likely to happen, I would have thought,” McCall said.

“When you have been out for a very long time, like he has, you try to get some volume in the legs.

“He has done for months now. Then it is into rugby sessions which are a little bit different. He looked good today (Wednesday) until he had to stop. He stopped halfway through.”

England can ill-afford any further losses as they contend with an escalating list of absentees for the June trip to South Africa.

Dylan Hartley, George Kruis, Nathan Hughes, Courtney Lawes, Jonathan Joseph and Anthony Watson have been ruled out for the entire season, while Bath have implored Jones not to pick Sam Underhill as he continues his recovery from a toe injury.