Republic of Ireland manager Martin O'Neill fears "every single" potential opponent in the World Cup play-offs, but after eliminating Wales, he thinks few teams will want to face his side.

Ireland won 1-0 in Cardiff on Monday courtesy of James McClean's 57th-minute strike to take second place in Group D at Wales' expense and secure one of the eight berths in next month's European play-offs.

Italy and European champions Portugal are among the teams Ireland could face, but after becoming the first opposition manager to prevail in a competitive game at Cardiff City Stadium in over four years, O'Neill was upbeat.

"I don't think everybody would want to play us," he told reporters.

"Do I fear teams? Absolutely. Every single one of them. I've always feared teams. That's the way to be. Then we go out and beat them. Or so I try.

"I don't think anybody would want to play Italy or Portugal, although Portugal might beat Switzerland (and qualify automatically).

"And there's about six others I'd rather not have. But I am delighted to be in it."

O'Neill played down the chances of injured pair Seamus Coleman, his captain, and Jon Walters returning to fitness in time for the two-legged November play-offs, the draw for which takes place on October 17.

He hailed the "character" of his team and heaped praise upon West Bromwich Albion winger McClean, who had previously scored vital goals in away wins over Moldova and Austria.

"He's just been magnificent," O'Neill said.

"His energy -- when you see James getting tired in a game with 10 minutes to go, you realise the rest of the players must be really tired because James just keeps going.

"But it wasn't that. His drive and determination have been a trademark for us. He's been magnificent in the tournament for us, absolutely magnificent."

Ireland's goal followed good work by Jeff Hendrick, who charged down a clearance by Welsh skipper Ashley Williams and crossed from the right for McClean to crash a first-time shot past Wayne Hennessey.

Beaten manager Chris Coleman said he was "absolutely gutted" and predicted the nation would be "in mourning" after Wales fell short in their attempt to reach a first World Cup since 1958.

Coleman, who led Wales to a stunning semi-final finish at Euro 2016, is out of contract at the end of the current season and he was evasive when asked if he might decide to stay on.

"I can't say right now about my future because I'm not thinking about it," he said.

"There's a chance I can, there's a chance that I won't. I can't give anybody an answer right now. It's not just a matter of me signing a new contract.

"There'll be a conversation now. There's a friendly next month. My contract's until the summer. We'll see.

"Right now I'm thinking about what we've just experienced. I want to go back with my family and my friends, take a bit of time with my children. When the dust settles, we'll see where we're going."

Already missing talisman Gareth Bale through injury, Coleman also lost key midfielder Joe Allen to a suspected concussion before half-time, but he absolved Ireland's players of blame.

"I said before the game it would be physical. We certainly didn't get disappointed," he said.

"But no complaints about their players or the physicality of it. It is what it is.

"Good luck to them. They've won it and I hope now they go on and qualify. All our players are all right. Joe's had a bang on the head, but he'll be OK."