The Springboks will take a 1-0 lead into the match in Bloemfontein after an added-time Damian Willemse penalty snatched a 32-29 first Test victory this weekend.
Also Read: Willemse knocks over late penalty as Boks edge Wales in Loftus thriller
World champions South Africa were woeful in the first half and trailed by 15 points at half-time before a personnel change turned the tide in Pretoria.
Jantjies was taken off during the break and veteran Willie le Roux came on at full-back, allowing Willemse to move to fly-half, where he impressed.
After the close shave against opponents eight places below top-ranked South Africa, coach Jacques Nienaber indirectly criticised Jantjies when he said “our kicking game was not functioning”.
“It is probably the one reason why we struggled to get out of our half (in the first half). It is probably the one thing we will have to improve.”
Pollard, who kicked 22 points in the 2019 Rugby World Cup final triumph over England in Japan, missed much of the first Test build-up due to French Top 14 commitments with champions Montpellier.
But handing the No. 10 shirt to Jantjies was a gamble as he had not played for Japanese club Docomo Red Hurricanes since December due to an injury and was arrested two months ago after an airline incident.
Also Read: Bok flyhalf Elton Jantjies to stay in squad — for now
Jantjies was detained at the main airport in Johannesburg after allegedly causing malicious damage to property during a flight from Dubai, but the case was later provisionally withdrawn.
Another Springbok star set to return for the potentially series-clinching second international is 2019 World Rugby Player of the Year and flanker Pieter-Steph du Toit.
Du Toit suffered a serious shoulder injury midway through the series against the British and Irish Lions last year and only returned to action in Japan last January.
Another injury prevented him being fully involved in training for the first Test, but the loose forward is likely to be available for Bloemfontein and could replace Franco Mostert.
While Nienaber likes to ring the changes early in the second half of matches, the decision to pull off captain Siya Kolisi after only 51 minutes was significant.
Kolisi, who skippered the Springboks to their third World Cup title and became an instant national hero, has not been overly impressive recently playing for the Sharks in the United Rugby Championship.
The player in the middle of the back row, Jaco Wiese, was voted man of the match as he continues to stand in for veteran Duane Vermeulen, who is recovering from surgery.
Scraping a three-point win Wales, who had only 12 men on the field for several minutes late in the second half due to yellow cards, came as a shock to South Africans.
Also Read: Four talking points: Bench claws Springboks back from the dead
TV analyst and former Springboks coach Nick Mallett said before the series that it would be a “massive disappointment” if the hosts did not win by at least 15 points.
Wales had lost all 10 previous Tests in South Africa, including a 96-13 thrashing in Pretoria 24 years ago
Download our app and read this and other great stories on the move. Available for Android and iOS.