Johnny Sexton has fired a warning shot to Ireland's rivals that Joe Schmidt's men have not even peaked yet, despite their stellar 2018.

Fly-half Sexton spearheaded Ireland's third Six Nations Grand Slam and helped head coach Schmidt's side topple back-to-back world champions New Zealand 16-9 earlier this month.

The 33-year-old was the overwhelming favourite to land World Rugby Player of the Year 2018, and on arrival at the ceremony in Monte Carlo laid bare Ireland's raw ambition.

The Irish will step into 2019 second in the world rankings bidding to retain their Six Nations crown and go beyond the World Cup quarter-finals for the first time in Japan.

And Leinster star Sexton insisted Ireland are not yet anywhere near their best.

"It's been an incredible year for Irish rugby, to win everything we could, really," Sexton told Press Association Sport.

"It's been very special, and a few of us have ended up here tonight.

"There are areas we've definitely highlighted to improve, which will be important in World Cup year.

"Teams try to peak for World Cup years. People ask have we peaked too soon? We haven't peaked, so we're just getting better and hopefully we can continue to do that.

"You have to improve ahead of the general curve. We know everyone else is going to get better.

"We'll be going into a lot of games now as favourites after what's happened this year, so that will be a challenge for us.

"We've got to deal with being favourites and I'm sure we can do that."

Ireland completed a second successive autumn Test series clean sweep with Saturday's 54-17 win over the USA in Dublin.

Sexton and Ireland's frontline players stepped aside as Ireland looked to build depth, the top stars still on a high from just their second win over New Zealand.

Head coach Schmidt is set to announce his decision on his long-term future next week, with the Kiwi expected to return to his native New Zealand after the 2019 World Cup.

The 53-year-old will be on hand with Ireland at least until his current contract expires after next year's global tournament however, with Sexton hailing him as the biggest influence on his career.

Asked to sum up Schmidt's role in his progress, Sexton replied: "That would be almost impossible to put into words.

"I've worked with him for eight years, and I can't speak highly enough of him.

"In terms of helping me as a player, no one's had a bigger influence on my career.

"There are obviously other influences, but it's been an incredible journey with him, because that's what it's been.

"He came into Leinster, we got to six finals in three years, we won four, lost two.

"He joined Ireland, we ticked off a lot of boxes. But there's still one more box to tick and hopefully we can keep building towards that World Cup."