The Chelsea forward had to come off in the 65th minute of the 2-0 Group B tie in Malabo, clutching his thigh. And Elephants manager Francois Zaoui fears the worst.
"This is upsetting," said the manager. "He's been a pivotal player for us since we began our warm-up matches. He scores goals and sets up goals and that's why it's going to penalise us.
"We're worried that he's suffered a strain or a tear because he pulled up so suddenly. We'll find out more after a scan."
But tests carried out today apparently revealed nothing untoward. "It was more a scare than any damage, Kalou felt pain behind the thigh but it's not a hamstring or tear," said the team's press officer.
Kalou set the Ivorians on their way to victory on Wednesday, scoring the opener on 16 minutes, having set up his Chelsea team-mate and captain Didier Drogba for the only goal of the game against Sudan last Sunday.