Speaking in his pre-match conference prior to Saturday's trip to Leicester, Koeman revealed that the former FC Twente star is still battling the problem.
"I spoke to Dusan and he was struggling a long time with a groin problem and we said okay, we have to stop now," said Koeman.
"We can't continue like this because maybe you have in pre-season the same problem for next season.
"It's going better but going slowly and maybe yes (he will be out for the season), but we will see."
The Serbian midfielder has scored four goals and provided seven assists in 31 league appearances in his debut season at the St Mary's Stadium.