Johnny Sexton has said it will take "a long time" before Ireland can forget the agony of their Rugby World Cup exit in Japan.

Ireland bowed out at the quarter-final stage for the seventh time after a 46-14 defeat by New Zealand in Tokyo.

"It'll be hard to get over, it'll be a long time," said fly-half Sexton.

"We haven't sat down and talked about it, ultimately we didn't do the basics well enough against New Zealand, but it'll be tough to live with."

After winning the Grand Slam in 2018, Ireland struggled to hit the same heights during Joe Schmidt's final year in charge of Ireland.

A third-placed finish in the Six Nations was followed by the record 57-15 defeat by England at Twickenham in August and, while that was followed by back-to-back wins over Wales, Ireland suffered a shock World Cup Pool A loss to Japan before being humbled by the All Blacks.

While Sexton argues that Ireland have not regressed, he admits they have not evolved as much as maybe they could have after a golden 2018.

"We felt there was a lot more left in us," reflected the Leinster captain during Tuesday's European Champions Cup launch in Cardiff.

"I don't think we ever went backwards from that point, but we probably just didn't evolve as much as we should have or could have.

"We got to where we wanted to get to, which was that quarter-final. I know it was against New Zealand and not South Africa, but either of those games were going to be incredibly tough.

"We knew we had to produce our best performance to get past it and we didn't come close to it. They were excellent on the day, it's as simple as that.

"There's going to be hundreds of conspiracy theories and people wanting to give their opinion, but that's the bottom line."

'Schmidt changed the expectations of Irish rugby'

Sexton also defended Schmidt, saying that he was 'baffled' by people who claim that the coach's legacy is tainted by the defeat by the All Blacks.

Schmidt brought the curtain down on his six-year tenure as Ireland boss following the World Cup exit.

"You just think about the success he's had, he has the best win percentage by a country mile," he said.

"He's changed the expectations of Irish rugby, of Irish supporters. He did it in Leinster and did it again and if we had done what he asked of us in the quarter-final, would we have won it? We'll never know because we didn't do it.

"We should take the majority of the blame as players, but his legacy in the players' eyes will always be there."

Sexton and Leinster begin their Champions Cup campaign at home to Benetton on Saturday, 16 November before a trip to France to face Lyon on 23 November.