Chiedozie Ogbene was set to be out to be for up to eight weeks with a knee injury.
But it has turned out to be disastrous as following surgery on Monday it has been revealed the flying winger will not play again in 2020.
That represents a massive blow to the Millers who based their game on Ogbene’s pace and power on the right wing.
Ogbene suffered cartilage damage in a training session on Friday and is now out for at least four months.
Warne said: “He won’t return for us for a minimum of four months and that is without any problems. We won’t be seeing him this side of the New Year that is for sure.
“They’ve managed to repair his cartilage which is good news for Chieo in the long-term, however it means that he is out longer now.
“We all sent him a video message before his operation on Monday, wishing him the best of luck. He sent me a text yesterday thanking everyone for their support.
“It’s really sad and I know its next man up but he is one of our most influential players. He gets us up the pitch and creates mayhem.
“It’s disappointing for him, but we’re all here for him to help him through it.
“The physios and fitness coaches are brilliant here so he’ll come back.
“Mental attitude is essential in life and he’s definitely got a really positive one.”