Ireland captain Roy Keane, his side's World Cup linchpin, threatened to fly home for "personal reasons" but later calmed down and decided to remain with the team.
Irish coach Mick McCarthy said on Wednesday he had contacted Colin Healy, the Celtic midfielder, and instructed him to get on the next plane to Japan to take Keane's place.
But a few hours later Keane, who has been troubled by hamstring and knee injuries, informed McCarthy at Ireland's Pacific training base that he would be staying.
"Roy came to me after training yesterday and said he was going home," McCarthy told Irish reporters.
"I knew he had been worried about his knee, that is an ongoing situation, but he told me he had personal reasons which he wouldn't go into. It was an enormous shock.
"I was told there was nothing I could do to change his mind. The decision was made. He was going home, that was it." "I rang Colin Healy and told him he was in. I had to ring him back a few hours later and tell him to change his plans but we have placed him formally on standby with FIFA in case there are further developments.
"No matter what happens, I'll invite him out to the tournament."
McCarthy is confident the scare is now over.
"I feel he's (Keane) made up his mind to stay, which is good, but you'll have to talk to him.
"He understands how big this story is and that he'll have to explain his actions to the media.
"I'm not annoyed with all this. It comes with the territory," McCarthy said.
Ireland are in group E with Germany, Saudi Arabia and Cameroon. The World Cup finals open on May 31