A win for City in the final match of the Barclays Premier League season would secure them the title but they face a QPR side still fighting for top-flight survival.
Since Mark Hughes took over at Loftus Road in January Rangers have only collected one point on their travels, but Mackie believes the pressure on the City players could be costly.
"They've not been in that position for a long, long time," he told QPR's official website.
"Not many of their players would have won the Premier League before - pressure does really strange things to people.
"We've been really poor on the road this season, but it's got to change at some point."
Following Djibril Cisse's late winner against Stoke last weekend, QPR now have their destiny in their own hands and a point against Roberto Mancini's side would confirm their survival and make for a tense finish at the top of the table.
"Everybody is expecting a big day for Man City," Mackie said. "But for us, we're scrapping for our lives and a point would mean the world to us."
Many people already believe the title belongs to City as they prepare to defend their unbeaten home record against struggling QPR, with main challengers Manchester United travelling to Sunderland knowing they need a favour from former player Hughes.
But the underdog tag suites the R's, according to Mackie.
"We feel we can go there and spoil the party. People have already written us off and think City are going to have a massive day," he said.
"But we're focused on trying to get something out of the game. It will be nail biting stuff, but I can't wait for it."