England number eight Billy Vunipola refractured his arm during England’s defeat by South Africa on Saturday.
The 25-year-old only returned to action in April after four months out with a broken right arm.
Vunipola was forced off with the injury before half-time in Bloemfontein, six months after first breaking his arm in Saracens’ European Champions Cup tie with Ospreys.
He will return to London on Sunday for further assessment.
More to follow.