Rhys Thomas is Wales coach Gatland's fourth-choice hooker
Wales have summoned Cardiff Blues hooker Rhys Thomas to South Africa to replace the injured Matthew Rees.
Rees will be out for two weeks after suffering a calf muscle strain in Saturday's 43-17 loss to the world champions and has been sent home.
Coach Warren Gatland has called up Thomas as a back-up to Richard Hibbard, who came on for Rees in Bloemfontein.
Wales forwards coach Robin McBryde said: "We're lucky that Rhys is familiar with life inside the squad."
Rees's injury is a further blow to Gatland, whose under-strength squad is already missing Grand Slam heroes Martyn Williams, Mike Phillips, Gavin Henson, Lee Byrne, Dwayne Peel and Alix Popham.
Rees only started for Wales in the Vodacom Stadium after Huw Bennett withdrew from the two-Test tour with an ankle injury.
Thomas, who is expected to arrive in Johannesburg on Monday, won the last of his 26 caps as a replacement in last November's defeat by South Africa at the Millennium Stadium.
Ospreys star Hibbard is set to start in Saturday's second and final Test but Thomas has been told he could feature in Pretoria.
McBride admits: "It won't be easy for Rhys slotting straight into the tour but he's an excellent player and he'll be ready to play a part on Saturday.
"Rhys knows the squad and so we're confident that he'll be able to adapt quickly."
Rees hobbled off in the 56th minute of Wales' mauling by the Springboks after suffering the injury during a tackle.
The 27-year-old went for a scan in a Bloemfontein hospital immediately after the game when it was confirmed he will be out for two weeks.
McBride acknowledged: "This is a big disappointment for Matthew, especially as he's an important part of the team right now.
"He's enjoyed a good tour so far and we know he has definitely benefited from the experience of playing in South Africa."