Carlos Carvalhal’s charges will be aiming to get their play-off push back on track, having gone four matches without victory.
It is a second South Yorkshire derby in four days for Wednesday, who were held to a 1-1 draw at Barnsley on Saturday.
But the Owls will fancy their chances of picking up maximum points against a Millers side who are rock-bottm and head into the contest on the back of an eight-match losing run.
Fox told The Star: “It’s been tough for Rotherham but I know they won’t stop fighting to the end. It could turn into a bit of a scrap.
“Derby games are often 100 miles pile per hour all over the pitch.
“We should have got three points at Barnsley so we will be looking to put that right at Rotherham.”
Time is running out for Wednesday to reclaim a play-off place, but former Charlton Athletic defender Fox remains confident the team can quickly turnaround their fortunes.
“I wouldn’t be too negative about the run that we are on,” he said. “We know we are good enough to beat anyone in this league.
“The key’s not to change too much. We just need to stick to what we know.
“We always look forward to the next game and Rotherham is another good chance for us to get a win on the board.
“They know their fate so it might be a weight off their shoulders and they might come out and play.
“We are going to treat it like any other game. It doesn’t bother us what their fate is. We are going to focus on ourselves and we know what we have got to do to win.”
At his press briefing yesterday, Carvalhal cited injuries to Wednesday’s offensive players as the main factor behind their style change this season. The Owls have struggled to replicate the free-flowing football they produced last year.
Carvalhal , who will be without the services of Sam Hutchinson (calf), said: “When we lose players who link the game at the same time, we miss something in the team. If we will cook something, you buy good tomatoes, good potatoes, and good rice, but if don’t have the fish, you eat more potato. A potato cannot play the role of fish.”