Huge controversy surrounded Switzerland's 1-0 first-leg win at Windsor Park on Thursday after the visitors were awarded a penalty when the ball appeared to hit the back or shoulder of Corry Evans.
AC Milan left-back Ricardo Rodriguez converted the spot-kick comfortably to give the Swiss a crucial away goal and move one step closer to qualifying for the 2018 World Cup in Russia.
Northern Ireland have a huge task ahead of them going into Sunday's second leg in Basel and they will be looking to become the first European team to progress via the World Cup play-offs after losing the first leg at home.
The fall-out from the controversial penalty is still rumbling on and O'Neill has called for his side to use that injustice as extra "motivation" to book their place on the plane to Russia.
"We are a little bit of a victim and we have to use it in that way and we will see how the Swiss deal with it on their home territory," he said. "We have to deal with the decision and put it to the back of our minds and use it as a motivation."
Kyle Lafferty and Josh Magennis were crucial for Ireland in the group stage, scoring three goals each, and punters may decide to use their free bet on the Green and White Army duo firing their side to glory.
Switzerland have never lost to Northern Irish on home soil, with the only two encounters ending in a 2-1 win back in 1964 and a 0-0 draw in 2004.