ADELAIDE United leftback Cassio could be back for the start of the new season after scans revealed that his left knee injury was not as serious as initially feared.

It was thought the 28-year-old could be out for up to nine months after suffering the injury during a friendly against MetroStars last month, when he lost his footing, causing his left knee to buckle.

Early indications suggested that he had suffered ligament damage to his left knee, similar to an injury that he sustained in 2003, and that he would need to undergo a full knee reconstruction.

However, new MRI scans taken in Brazil revealed there is no rupture in Cassio's anterior cruciate ligament and he does not require surgery.

"We got a copy of the MRI scans and our surgeon had a look today and confirmed there is not a rupture," said Adelaide United football director Michael Petrillo.

"The doctors here are satisfied with the diagnosis of the specialists in Brazil and Cassio is now undergoing rehabilitation in Brazil where his recovery is at a well advanced stage."

Adelaide United coach Aurelio Vidmar was delighted by the news.

"The initial MRI scans that were taken in Adelaide were not very clear because of the swelling in his knee at the time," Vidmar said.

"From what he has told us from over in Brazil, he says he should be back for the start of pre-season which would be remarkable."

Cassio will continue his rehabilitation in Brazil before returning to Adelaide in mid-June to prepare for the new A-League season.