Vermaak is hoping to impress with the Lions series just weeks away
South Africa coach Peter de Villiers will take a look at six uncapped players ahead of the Lions series when his side face a Namibia XV on 29 May.
The Springboks have called up Steven Sykes, Jean Deysel, Wian du Preez, Jano Vermaak, Morgan Newman and Earl Rose for their only pre-Lions warm-up game.
Established stars like captain John Smit, flanker Schalk Burger and wing JP Pietersen are also in the 23-man squad.
The Lions fly to South Africa on Sunday with their first game on 30 May.
De Villiers is without injured fly-half Ruan Pienaar, while centre Jaque Fourie is getting married on 30 May.
Meanwhile, Bulls players were not considered for selection because of their involvement in the latter stages of the Super 14.
Smit, who captained South Africa to glory in the 2007 World Cup, said he was driven on by a huge fear of failure as the Springboks attempt to make up for their 1997 series defeat by the Lions.
"I'd be lying if I told you I wasn't scared of failing against the Lions," he told SA Rugby magazine.
"The fear of failure is with me in everything I do. I'm sitting here talking to you and feel that fear creep up inside me. But I've learnt that it's how I manage that fear that will determine my success or failure.
"You have to understand how fine the line is between a lifetime of regret and having an enduring memory of success in a Lions series."
Meanwhile, De Villiers said the game against the Namibian XV in Windhoek would be key to the Springboks' chances of success in the much-anticipated series.
"Without the opportunity of a few warm-up games we must ensure that we get the most out of this match, regardless of the fact that some players are not in attendance," he said.
"After this match we will assemble a Springbok squad that will have three weeks to prepare for the first Lions Test and we have to maximise the time we have at our disposal."
South Africa training squad:
Backs: Odwa Ndungane, Jongi Nokwe, JP Pietersen, Jean de Villiers, Adi Jacobs, Morgan Newman, Peter Grant, Earl Rose, Ricky Januarie, Jano Vermaak
Forwards: Ryan Kankowski, Juan Smith, Heinrich Brussow, Jean Deysel, Schalk Burger, Andries Bekker, Johan Muller, Steven Sykes, John Smit, Adriaan Strauss, Bismarck Du Plessis, Tendai Mtawarira, Wian Du Preez.