Lock Van der Merwe injured his ribs during the 39-20 loss to Australia on Saturday, while flanker Brussow is sidelined with a hamstring strain.
Full-back Gio Aplon is suffering from back and shoulder injuries after falling awkwardly against the Wallabies and is a doubt for the contest against the All Blacks in Wellington.
The Springboks are missing over 20 front-line players and were further weakened when lock Johann Muller returned home due to a hamstring complaint.
Muller's place in the squad was taken by uncapped second row Gerhard Mostert, but Van der Merwe will not be replaced as coach Peter de Villiers says his side have "run out of locks".
South Africa were well beaten in their Tri-Nations opener against the Wallabies and now have to travel to the odds-on tournament favourites with severely depleted ranks.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.