South Africa and Australia will look to seal the final berth when they face off in the seventh ODI match of the tri-series at Kensington Oval in Bridgetown on Sunday.
South Africa lead the three-team standings with 10 points, with Australia second on nine and the West Indies on eight.
Each team has two wins and two losses, with South Africa ahead due to bonus points and a superior net run rate.
South Africa entered this match with a mammoth win over West Indies, anchored by Imran Tahir and Hashim Amla.
Amla struck 110 off 99 balls and legspinner Tahir claimed a record haul of 7 for 45 as South Africa defeated the West Indies by 139 runs.
SA's total of 343 for 4 in 50 overs was built around an opening stand of 182 between Amla and Quinton de Kock, who scored 71 off 103 balls. Faf du Plessis contributed an unbeaten 73 off 50 deliveries.
The 37-year-old Tahir became the first South African to claim seven wickets in a one-day international, and his figures were the ninth-best of all time.
Other batsmen such as Quinton de Kock and Faf du Plessis made telling contributions as well. Tabraiz Shamsi played an efficient second fiddle to Tahir in the bowling department.
With figures 7 for 45 Tahir registered the record for best South African bowling figures in ODIs.
"Barbados, I've been told, is a better batting wicket with a bit more bounce. I also believe the boundaries are also a bit bigger. Who knows, do we go in with three spinners, is that an option?," South Africa bowling coach Claude Henderson told Cricinfo.
Barbados is expected to be a better batting surface.
On the other hand, Australia team management in confident and said Steve Smith will play against South Africa on Monday despite sitting out training for the second consecutive day due to a thigh problem.
On Friday, the Australian side had a full two hours fielding session before their main training session on Saturday and Smith was a spectator for both the sessions.
The Australian skipper experienced tightness in the right quad during their previous match against West Indies in St Kitts last Tuesday and had his leg strapped by physiotherapist David Beakley during the match. But he was clearly unaffected during the game at Warner Park, posting a polished 74 before fielding during the run chase.
He had been expected to bat at Saturday's training but despite missing out again, he's confident of batting in the nets on Sunday and is considered in no doubt for the match against the Proteas.
"I know it's all precautionary and he'll be ready to go for Sunday's clash. I'm sure he's raring to go and to hit a few cricket balls, " fast-bowler Mitchell Starc was quoted by cricket.com.au.
With David Warner already ruled out of the series due to a broken finger, Smith’s side-line will only affect Australia’s chances of making it to the final of the Tri-Nation Series.
Australia: Steven Smith (capt), George Bailey, Nathan Coulter-Nile, James Faulkner, Aaron Finch, John Hastings, Josh Hazlewood, Travis Head, Usman Khawaja, Nathan Lyon, Mitchell Marsh, Glenn Maxwell, Mitchell Starc, Matthew Wade (wk), Adam Zampa.
South Africa: AB de Villiers (capt), Kyle Abbott, Hashim Amla, Farhaan Behardien, Quinton de Kock (wk), JP Duminy, Faf du Plessis, Imran Tahir, Morne Morkel, Chris Morris, Wayne Parnell, Aaron Phangiso, Kagiso Rabada, Rilee Rossouw, Tabraiz Shamsi.