Glamorgan Wanderers are forced into two changes from the side that beat Newport for the trip to Carmarthen.
Tom Evans and Mike Grimes are out of the pack and in come Richard Thomas and Lee Highgate.
On the bench Matt Trowbridge returns after missing two games through injury and scrum half Rhys Dyer gets a place in the squad for the first time this season.
Dan Fish, who has impressed everyone this season, continues at fullback and he has been rewarded for his efforts with a place at the Blues academy.
Glamorgan Wanderers: 15. Dan Fish 14. Rory Budina 13. Charlie Johnson 12. Robin Lock 11. Ryan Healey 10. Scott Sneddon 9. Harry Trelawny; 1. Nathan Trevett 2. Ieuan Davies 3. Scott Andrews (capt) 4. Richard Thomas 5. Gareth Knight 6. Lee Highgate 7. Ben Rose 8. Josh Navidi
Replacementa: 16. Ieuan Dobbs 17. Mark O'Leary 18. Dan Partridge 19. Carl Kimber 20. Lee Highgate 21. Steve Cullen 22. Rhys Dyer
Wales reached their first semi-final since 2013 in the opening round of this season's HSBC World Rugby Sevens Series in Dubai. WRU TV's Graeme Gillespie recaps on what proved to be an eventful tournament
Wales and Ospreys back row James King, who came through the North Wales age grade system, nominated North Wales Regional Community Rugby Manager Marc Roberts, in the WRU's 'Diolch' initiative where squad players thanked those who played a part in their rise to the top.
Beating Merthyr has boosted Carmarthen Quins hopes of reaching a top eight spot in the Principality Premiership. Quins captain Haydn Pugh is delighted with his team's progress and is determined that everyone from the Under 6s through to the senior team, enjoys the ride.
When the Wales squad were asked to nominate individuals who played a big part in their early playing days, Wales and Dragons full back and wing Hallam Amos thought of his former Monmouth School rugby coach John Bevan.
Sam Cross and Luke Treharne have been named as co-captains of the Wales Sevens side as head coach Gareth Williams names his 12-man squad to play in the first leg of the HSBC World Series in Dubai next weekend.
Bedwas head coach Steve Law and players Nicky Griffiths and Alun Rees extol the virtues of the close knit club as they prepare to host third place RGC 1404 - who are one place head of them on the Principality Premiership points table - on Saturday.
Many of the Wales squad have said Diolch (thank you) to someone who played an important part in their early playing days by nominating them to be invited to the Wales v South Africa match. One person, Gowerton Comprehensive geography teacher Mr Dean Mason was nominated by two of his former pupils, Dan Biggar and Sam Davies.
The second WRU disability rugby pilot has been delivered, this time in Caerphilly schools, culminating in a festival at the Caerphilly Centre of Sporting Excellence, Ystrad Mynach tomorrow. Plans are in place to set up a Disability Rugby Club in Newbridge to provide long-term playing opportunities.
WRU TV: Hear from inside the Wales camp as Neil Jenkins discusses this weekend's clash with South Africa and how the squad are looking to put in a strong performance to round of the 2016 Under Armour Series