Niall Quinn is prepared to surrender his World Cup dream and pull out of Mick McCarthy's squad if he is not 100 percent fit.
The Sunderland star - plagued by back trouble - said he "could not live with himself" if he took another striker's place in the squad when he knew he was not at the peak of his fitness.
Quinn, who missed Thursday's World Cup play-off second leg against Iran in Tehran with injury, told BBC Radio Five Live's SportsWeek show: "I'll have to be honest and not take someone's place if I'm not fit.
"I couldn't live with myself if I took someone's seat. If I can do a job for Mick and he needs a target man as an option, I'll be there - if I'm fit.
"Playing in the World Cup means your life will actually change - as players will become star names. Robbie Keane's a good player, and if he goes and has a good World Cup, the sky's the limit for him.
"I'm actually so shocked we've qualified that it really hasn't sunk in yet. It's an enormous relief and the result of years of hard work.
"Whatever happens in the World Cup, we'll have a good time."
Quinn also revealed the emotional stress of watching his team-mates decide the Republic's World Cup fate on Thursday left him exhausted.
"I've never witnessed anything like the atmosphere in the stadium in Tehran in my life," he added.
"I was physically and mentally drained by the time we got into the dressing room afterwards."
PA