With games running out, the Sky Blues dropped to 20th in the Championship table after a 2-1 defeat at Scunthorpe on Saturday.
Said Coleman to the CT: "QPR is now our biggest game of the season - it's as simple as that.
"These remaining games are cup finals for us and unless we go into them harder and tougher, we will be going down.
"Relegation can happen to anybody - ask Sheffield Wednesday - they're a big club and they went down. It can happen if we continue like we did at Scunthorpe."