Van Niekerk will be covered by AJ Venter

All three players failed fitness tests on Saturday ahead of the Springboks' warm-up Test against the Pacific Islands on 17 July.

None of the players have been replaced although Van Niekerk may return if he comes through a club match on Saturday.

South Africa begin their Tri-Nations against New Zealand on 24 July.

On Friday, South Africa recalled back-row forward AJ Venter to the squad just 24 hours after axing him in order to cover Van Niekerk's absence.

Venter had just returned from an eight-week suspension for head-butting.

Meanwhile, full-back Werner Greeff failed to report to the Springbok camp on Sunday with a spokesman admitting they were unaware of the player's whereabouts.

South Africa Tri-Nations squad:

Backs: Bolla Conradie, De Wet Barry, Neil de Kock, Jean de Villiers, Fourie du Preez, Gaffie du Toit, Werner Greeff (possible), Marius Joubert, Wayne Julies, Percy Montgomery, Breyton Paulse, Brent Russell, Jaco van der Westhuyzen

Forwards: Eddie Andrews, Bakkies Botha, Gerrie Britz, Schalk Burger, Danie Coetzee, Jacques Cronje, Quinton Davids, Os du Randt, Victor Matfield, Faan Rautenbach, Hanyani Shimange, John Smit, CJ van der Linde, AJ Venter, Pedrie Wannenburg