Sri Lankan skipper Mahela Jayawardene said they do not know the extent of his injury.
"Nuwan is out of the series. He has got a groin injury. We cannot get a scan here. Once we get back to Colombo, we will get a scan done and see the extent of the injury and how long he will have to be out," Jayawardene said.
Kulasekara suffered the injury when he went for a catch, offered by Virender Sehwag, in the 11th over.
Kulasekara, who was fielding at mid-off, dived to pouch the mistimed shot by the Indian, but his effort did not help his side as TV replays could not suggest if the catch was taken cleanly.
Sehwag, who went on to make 96, was on 24 at that time.
Kulasekara did not bowl after the incident. He bowled five overs and took the wicket of Gautam Gambhir.
Jayawardene said the replacement will be discussed soon.
"We will talk to the selectors. The A team guys probably would have arrived today in Sri Lanka. There was a selector on that tour, so we will get some advice from him, who was in good form and try and come up with a replacement," he said.
