The game will be the club’s 12th match in the final 35 days of the regular Championship season, due to an exhaustive fixture backlog after a Covid outbreak forced the club to postpone three scheduled games in early March.
It followed earlier problems at Christmas which saw two games called off due to positive tests.
Without the crammed late-season schedule, Warne believes that the Millers would be a Championship club next season, regardless of events in the Principality.
Instead, only victory, coupled with Derby County failing to beat Sheffield Wednesday, will retain the club’s second-tier status.
Questioned whether Covid issues would represent the chief contributor in the Millers going down – should they fail to stay up – Warne said: “Yes, I do. We had those two weeks when the training ground was shut on two separate occasions and on the second occasion, I got tested positive with two days of the two weeks left.
“So I missed the training ground for three-and-a-half weeks. I am not saying that I am important, but for ten per cent of the season, I was not even here.
“I honestly think our performances have been good. I don’t necessarily think we would have won lots more games.
“But I just think the schedule has been punishing. It has been relentless.
“We would have given ourselves a better chance, put it that way. But we still have a chance and are fortunate that teams around us have struggled to keep us in it.
“We are in it a little bit by default, but if that is the door left open for us; we have got to try and be brave enough to walk through it.”
Millers chairman Tony Stewart has stressed that Warne will be in charge next season, if the club are relegated.
On his future beyond tomorrow’s game at Cardiff, Warne added: “I will have a couple of weeks (after Saturday) where I don’t think about football.
“I will be amazed if I ever come to the conclusion that I do not want to be the manager of this amazing club, but that might be taken out of my hands. But at the moment, I enjoy the job and give everything I possibly can.
“I have the chairman’s support currently, but I do know how football works.”
Support The Yorkshire Post and become a subscriber today. Your subscription will help us to continue to bring quality news to the people of Yorkshire. In return, you’ll see fewer ads on site, get free access to our app and receive exclusive members-only offers. Click HERE to subscribe.