The Millers make the short hop to Hillsborough for a game that pits the third-bottom visitors against the second-bottom hosts.
Rotherham go into Wednesday’s game on the back of five straight defeats while the Owls have lost their last three, but have a new manager in Darren Moore.
MacDonald said: “The belief is there. The lads believe in themselves, in the team, in each other. We’ve lost the last five games by one-goal margins, the last four by 1-0.
“You’ve got Bournemouth, Norwich and Reading in there - all top six. We’ve been in every game.”
“The gap has opened up a little bit but we’ve still got games in hand. We can take confidence and belief from some of our performances, we just need to start putting our chances away.
“Everyone wants to work for each other, as you can see from some of the performances. We have to take that into the next 15 games. Working for each other is first and foremost what we have to do and then hopefully the chances, the goals and the points will come.
“We’re not playing bad football. It’s not like we’re not creating chances and are getting battered 3-0 or 4-0 every week. It’s one goal here and there. It’s about the luck some teams get and some don’t.”
Tomorrow night could be a nervy occasion given what is at stake and how defeat for either side could feel like the first nail in the relegation coffin.
“It’s a six-pointer. It’s a massive game,” said MacDonald.
“The lads have got to really roll their sleeves up. We know what it’s about. It’s a big game. We can go there and get three points, I know we can.
“It’s just going to be a battle. You’ve got to win the battle first and stamp your authority on the game. If we do that, our quality can come through and hopefully we can create some chances and score goals.
“Hopefully this can turn around that bit of luck that we need to go into the last push of the season.”
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