The Millers hitman suffered a thigh injury during Saturday’s defeat to MK Dons and Warne is hoping for favourable news from the scan.
He is awaiting the results, but is planning to be without him for two weeks.
“Freddie has done his quad,” Warne said. “Hopefully the scan is kind on Monday but my educated guess is that he will be out for two weeks.”
Warne accepts his plans for Wednesday’s Papa John’s Trophy semi-final with Hartlepool might have to change after Saturday’s defeat.
The Millers suffered a big blow in their hopes of virtually wrapping up League One promotion as they failed to beat their 10-man opponents, who came from behind to win 2-1.
Instead of being 13 points clear of third-placed MK they are now just seven and with another potentially pivotal game at Wycombe on Saturday, Warne is keen to protect his most important players.
That will allow fringe players to get a game, including a possible debut for January signing Georgie Kelly with Ladapo and Will Grigg ruled out.
“The same players have played virtually every game and I thank them for their efforts,” Warne said.
“With Wycombe away to come on Saturday - which is even bigger game now - we are going to have to play some different faces.
“Georgie has an opportunity to get himself closer to the squad.”
Midfielder Jamie Lindsay missed Saturday’s loss with a shoulder issue, but he could be back in contention.
“He hurt his shoulder so that is a disappointment because he would have definitely provided an energy boost, Warne said.
“But he was taken out of the squad.
“Jamie should be okay for Wednesday, I think he'll get a scan and get his shoulder jabbed. He will be okay for Wycombe.”