Du Plessis will undergo surgery on his hips this week which will rule him out for the rest of the year.
Du Preez (torn pectoral muscle), lock Jan de Klerk (broken toe) and flank Cobus Wiese (shoulder) are all expected to return in three months time.
Hooker Siyabonga Ntubeni, centre Daniel du Plessis and flanks Rynhardt Elstadt and Steph de Wit will all return to full training next week.
Ntubeni makes his return from an Achilles injury sustained in the Currie Cup last year, whilst Daniel du Plessis was able to avoid undergoing surgery on his shoulder, which he dislocated against the Crusaders in Christchurch.
Elstadt has recovered from a fractured rib and De Wit is back after breaking his ankle in pre-season.
Centre Huw Jones’ hamstring is recovering well and he should be available to play in five weeks time.
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