Mendis, who returned the best figures by a bowler in T20 cricket with six wickets for eight runs in Tuesday’s match, went off the field soon after he had completed his quota of four overs.
“Mendis’ injury is our only worry ahead of tomorrow’s (Saturday) game against South Africa,” Sri Lanka team manager Charith Senanayake said.
“We are monitoring Mendis’ progress and will take a call on him before the match.”
Sri Lanka also have leg-spinner Jeevan Mendis, who took three wickets bowling in tandem with Ajantha against Zimbabwe, left-arm spinner Rangana Herath and uncapped spinner Akila Dananjaya in their squad.
South Africa captain AB de Villiers said even if Mendis played on Saturday, his team would not allow him to dictate terms.
“A guy like Ajantha Mendis is a world class bowler and when he’s going well he will always pick up wickets,” de Villiers said.
“But we’ve seen him perform under pressure and seen him break down under pressure as well so, hopefully, we can get the upper hand against him and not let him bowl to us.”
Both teams have already qualified for the Super Eight stage from Group C but would look to maintain momentum with a victory on Saturday.
South Africa, who thrashed Zimbabwe on Thursday by 10 wickets in their opening match, might make some changes to test their bench strength.
“We may give one or two of the other guys a run, but once again, we want to win the game, beat the home team in their conditions and pick up the momentum,” de Villiers said.
Sri Lanka captain Mahela Jayawardene also ruled out a dead rubber.
“We need to win and get momentum going,” Jayawardene said. “Probably their lower middle order is a little inexperienced. What we need to do is focus on our strengths.”
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