England No 8 Billy Vunipola will return home after re-fracturing his arm in the second Test against South Africa.
The Saracens forward suffered a recurrence of the injury which forced him out for much of last season and will return to London on Sunday for further assessment next week.
He was replaced towards the end of the first half of Saturday's 23-12 loss, which condemned Eddie Jones' side to a series defeat.
News of Vunipola's departure comes after it was confirmed on Saturday that Ellis Genge would return home due to a knee injury and that fellow prop Mako Vunipola, Billy's brother, would also return home for family reasons - as had been agreed beforehand.
Exeter's Alec Hepburn has been called up and will join the squad ahead of next weekend's third Test in Cape Town.