Defeat to Tottenham at the Madejski Stadium, courtesy of Robbie Keane scoring the only goal of the game in the 16th minute, dropped the hosts in the bottom three with one match left.
The game is against Derby but three points are not guaranteed as Reading have not scored in six matches.
Coppell said: "People remind you all the time that you haven't scored for so long and there is the confidence factor.
"Now it's win or bust next week, we have to get a result to give ourselves a chance.
"It doesn't matter who we play we have to win, we've lost the habit of winning football matches."
Spurs could have sealed the points by half-time but only had Keane's strike to show for it.
Darren Bent forced a save from Marcus Hahnemann when sent through and Steed Malbranque, a threat in midfield, made a mess of a close-range finish when he tried to backheel the ball in.
Keane's opener came after he was fouled by Michael Duberry but Howard Webb played advantage.
The Tottenham striker picked the ball up on the edge of the area and dummied around Kevin Doyle and Liam Rosenior before finishing.
Malbranque also had a goal disallowed before the break.
"At half-time I told them the effort was incredible - it was like they were trying to plait spaghetti - they worked so hard to stay in the game," Coppell said. "We just needed to restructure."
It got better for the hosts after the break, with Andre Bikey and Marek Matejovsky going close. Radek Cerny also had to save from Dave Kitson and Rosenior.
But after Spurs held on for the victory, Reading were left to contemplate a nerve-shredding end to the season.
Coppell admits he could have done things differently, including investing more in his squad.
He explained: "Since the chairman has come here he's built a self-financing club. That ultimately might be our downfall.
"I didn't spend so much last summer and in January, if it doesn't work it's my fault.
"The manager always gets the blame, when the team do well the players take the credit, my shoulders are broad enough and I'll take it."
Spurs head coach Juande Ramos paid tribute to Keane, who took his tally to 23 for the season, level with Dimitar Berbatov. Berbatov was absent with a groin strain and Keane took centre-stage.
"He is a magnificent player and we rely on him a lot," said the Spaniard. "His performance today was tremendous.
"He got the goal and was in a position that made it difficult for Reading.
"We played a good game, there were a lot of chances and we dominated play and should have finished the game off."