Ruddock goes into the match without first-choice midfield pairing Gavin Henson (groin) and Tom Shanklin (knee), while leading contender Sonny Parker is battling a hamstring injury. The Blues' Jamie Robinson is still finding his feet after a year out with a knee injury and the Dragons' Hal Luscombe is out of the equation after breaking a thumb against Edinburgh on Friday night.
Ruddock has the choice of the Dragons' Ceri Sweeney in the No. 12 jersey, while veteran Mark Taylor may earn a recall if Parker fails next week's fitness test. Skipper Gareth Thomas played at outside centre for Toulouse on Saturday and may move from fullback to fill the problem area.
World-class prop Gethin Jenkins (shoulder) will also miss the autumn Test series, while doubts linger over Lions star Ryan Jones after he injured a shoulder against Bath a week ago. Ironically, the man in the Bath No. 8 jersey that day is being tipped as Jones's replacement in the Wales lineup.
Gareth Delve has been tipped as a Wales star for several years, but a serious shoulder injury meant his 2003 match against the Barbarians is his only match in the red jersey. But after an eye-catching performance in Bath's Powergen Cup victory over the Ospreys, his name is back in the headlines.
"I got a text from Scott Johnson after the Ospreys game, asking if Gareth was available for Wales squad training," Bath coach John Connolly said. "Gareth is a big, strong man. He's incredibly athletic, he's a massive ball-carrier, a good defender and he has the physicality for Test rugby.
"I think Gareth will be involved in the autumn. Ryan Jones is a good player, but he took another knock against us so you don't know. And Colin Charvis is competing with Gareth - I think Charvis is an openside flanker. I think you'll see Gareth in the 22 for the autumn Tests."
Connolly said the most exciting thing about Delve was that he still had a lot of improvement in him after his horror run of injuries.
"Gareth is definitely on an upward spiral - he didn't play for three years and it's always going to take a year to come back into it," the Australian said. "He came into some form slowly last year and he's really stepping up to the mark this season. Against the Ospreys, he was the best backrower, and the best thing is that you know he has a lot of improvement in him."
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