Adelaide United midfielder Nathan Konstandopolous faces a year on the A-League sidelines because of a serious knee injury.

The 23-year-old has torn the anterior cruciate ligament in his right knee at training.

"This is a devastating blow ... the entire club feels for him during this very challenging time," Adelaide's football director Bruce Djite said in a statement on Thursday.

"Nathan is a talented footballer and a strong individual with fantastic character, so I know for sure he will come through this challenge and be back better than ever ... it will be a long and difficult road."

Konstandopolous will soon consult a surgeon with the prospect of a knee reconstruction operation.

The Adelaide-born central midfielder played nine A-League games this season, taking his career total to 53 since his debut in 2013/14.