If South Africa win the second and final Test in the series, and both home fixtures against Pakistan starting later this month, they will be guaranteed a place in the final.
They thumped Sri Lanka by 233 runs in the first Test in Durban, bowling them out for their Test record low of 42 in the first innings, but the wicket in Gqeberha may be more to the visitors' liking.
Traditionally lower and slower, the coastal venue provides more opportunities for spinners and was the scene of a historic eight-wicket victory for Sri Lanka in 2019 when they became the only sub-continent side to win a Test series in South Africa.
The hosts have lost allrounder Wiaan Mulder and fast bowler Gerald Coetzee to injury, and have called up 18-year-old speedster Kwena Maphaka as a replacement for the latter.
Whether he makes his debut remains to be seen, but he has a good chance with Dane Paterson the other seamer option in the squad.
South Africa could play an extra batter as a replacement for Mulder, or go with spinning allrounder Senuran Muthusamy.
The first Test win had several impressive individual performances.
Fast bowler Marco Jansen took career-best match figures of 11-86, including 7-13 in the first innings, while captain Temba Bavuma and the increasingly imposing Tristan Stubbs managed second-innings centuries with the bat.
Coach Shukri Conrad praised the mentality of his side after they claimed a fourth Test win in a row.
"We get on with things and what we continually tell the guys is that they need to be themselves on and off the field," Conrad said.
"They're just a great bunch who get on with it, they train hard, enjoy each other's company away from the field."
Sri Lanka needed to improve with the bat after their woeful first innings in Durban and did so by scoring 282 in the second.
"We have a very experienced unit, and they have been in situations like this before," batting coach Thilina Kandamby said. "I don't think the players are mentally down. We give them lot of confidence."
Sri Lanka can also reach the WTC final but will have to win in Gqeberha and beat Australia in two home Tests starting in January to stand a chance.
Meanwhile, Heinrich Klaasen will captain the Proteas in three Twenty20 matches against Pakistan next week, allowing Markram to concentrate on the Test series.
Marco Jansen, Keshav Maharaj, Kagiso Rabada and Tristan Stubbs will also sit out the T20 series because of their involvement in the Tests, but will play in the three One-Day Internationals between the two countries later in the month.
South Africa and Pakistan then meet in three ODIs on December 17, December 19 and December 22 before beginning a two-Test series on December 26.
South Africa T20 squad:
Heinrich Klaasen (capt), Ottneil Baartman, Matthew Breetzke, Donovan Ferreira, Reeza Hendricks, Patrick Kruger, George Linde, Kwena Maphaka, David Miller, Anrich Nortje, Nqaba Peter, Ryan Rickelton, Tabraiz Shamsi, Andile Simelane, Rassie van der Dussen.
