The Super League Group 1 is wide open after Sri Lanka beat South Africa by 29 runs at the Fatullah District Stadium.
Sri Lanka bounced back from defeat against the West Indies to beat South Africa, conquerors of India two days ago, with a solid batting display.
Sri Lanka won the toss and, for the first time in the tournament, batted first.
Liberated from the pressure of chasing a target, Sri Lanka's top order batsmen finally find found their form.
Opener Upul Tharanga dominated from the start to become the first Sri Lankan to reach the 100 mark in the tournament. Tharanga went on to make 117 and was well-supported by Nadeera Nawala (56) and Gihan de Silva (42) as South Africa's bowlers failed to reproduce the unerring accuracy they had shown in bowling out India two days earlier.
With all-rounder Chamith Kulasekara chipping in with 32 from 14 balls in the final overs, Sri Lanka recorded comfortably their biggest total of the tournament, an impressive 277 for 5 in 50 overs.
The South Africa reply got off to a stuttering start and Sri Lanka captain Farveez Mahroof and Manoj Chanaka picked up a wicket each in the opening five overs.
Jaco Booysen lead a spirited fightback as South Africa's innings gained momentum. They reached 200 in 39.4 overs with Booysen rapidly passing 50 and closing in on the second century of the match.
With five wickets and 10 overs in hand and 78 runs required for victory it looked as though South Africa were capable of engineering a third consecutive spectacular victory after beating England by one wicket and India by three runs.
But Mahroof brought himself and Chanaka back into the attack and they picked up vital wickets.
When Booysen was eighth man out, bowled by Mahroof for 120 from 114 balls, the game was up for his side and the tail was mopped up in the 49th over with South Africa still 29 runs short.
South Africa coach Russell Domingo felt his side had lost the match in the first innings.
"The Sri Lankans played very well in that they did the basics well," said Domingo.
"The same could not be said for us. We conceded 24 extras to their seven and dropped a couple of crucial chances."
Sri Lanka coach D.S. de Silva was relieved that his top order had at last made some runs.
"It was our batting that won us the match today," said De Silva.
"We made a big score for the first time and we will now look to be positive in the group decider against India. We are still confident we can make it through to the semi-finals."
Sri Lanka's next match is a day/night game against India on 26 February, South Africa will play West Indies on the same day.