Port Elizabeth - England spinner Jack Leach is to return home from South Africa on Thursday after battling a series of health issues, including a recent bout of sepsis, tour officials have announced.
He "has not been able to reach the expected levels of fitness to be considered for selection", it added.
The bespectacled Leach became a cult hero for his stoic resistance while Ben Stokes produced a match-winning innings in last year's third Test against Australia.
The third Test in the four-match series against South Africa starts at St George's Park on Thursday. The series is all square at 1-1.