Head coach Andy Farrell expects Ireland to be “a hell of a lot slicker” in their Rugby World Cup opener following some disjointed warm-up displays.

The world’s top-ranked nation are among the pre-tournament favourites and launch their campaign on Saturday afternoon against Pool B minnows Romania in Bordeaux.

In-form Ireland arrived in France on a 13-match winning run but having failed to fully convince during last month’s disjointed victories over Italy, England and Samoa.

Farrell is untroubled by those patchy performances – produced by largely experimental line-ups – and has backed his players to deliver when it really matters.

“It’s certainly not a concern because obviously (they were) three warm-up games with different personnel and everyone is at different stages in the pre-season,” he said.

“It’s all galvanised to one point and this is it: the start of the competition.

“The performance should be one that’s a hell of a lot slicker, let’s put it that way.

“Understanding what it’s all about and getting down to business is where we’re at at this stage. We’re looking forward to getting going.”

Farrell has named a strong starting XV for the curtain raiser, albeit world player of the year Josh van der Flier begins on the bench, while wing Mack Hansen has the weekend off, despite being available.

Fly-half Johnny Sexton is back from a three-match ban to captain Ireland, while rookie lock Joe McCarthy is among the six starting World Cup debutants.

Farrell’s 33-man squad contains a total of 18 players who have never played on the biggest stage.

The Englishman feels there are benefits to that scenario but also suggested some of the newcomers need to avoid distractions better than they did around the recent Samoa game in Bayonne, when Ireland were based in nearby Biarritz.

“It’s an advantage because of the youthfulness and the quality of those players is top drawer,” he said.

“But they also need to understand what it is that they’re coming into.

“The reason we went there (to Biarritz) is that there’s a lot of distraction that goes on, certainly when you’re in a hotel that’s on the beach.

“Some people handled that brilliantly, some people didn’t. Learning from those experiences is pretty important because you don’t get second chances after this in World Cups.

“You have to wait four more years – if you’re lucky enough.”

Unfancied Romania are ranked 19th in the world. Farrell is braced for a physical assignment amid temperatures forecast to reach around 35 degrees Celsius.

“For anyone that’s watched them, it’s pretty clear and obvious that they’re a determined group,” said Farrell.

“I think by their own recollection they would say that their point of difference is their power, their aggression, their set-piece.

“They love mauling, they love the scrummaging part of the game. They’re very direct in the forwards and pretty nippy and dangerous within the backs as well.

“We’ve scouted them well but, at the same time, more of the concentration this week has been on ourselves.”

Corey Domachowski believes that Wales can reap the rewards from “15 weeks of hell” in their Rugby World Cup campaign.

The Cardiff prop is a Test rugby newcomer, making his debut against warm-up opponents England last month.

His impact was sufficient for Wales head coach Warren Gatland to select him not only in the final World Cup squad, but also hand him a place among the matchday 23 to face opening World Cup opponents Fiji on Sunday.

Wales have moved south from their Versailles training base to the first match venue of Bordeaux.

They were greeted by temperatures of 35 degrees as the heat in France shows no sign of relenting, and even though Sunday’s encounter does not start until 9pm local time, it is set to be only eight degrees cooler.

Wales, though, are fully prepared, with the players being put through their paces at punishing pre-World Cup camps in Switzerland and Turkey during a training phase that began in late May.

“We’ve trained hard for this,” Domachowski said.

“We had 15 weeks of hell, to be honest. It has been absolutely savage.

“And I genuinely think if we put what we’ve done on the training field on to the playing field, then we are going to be a tough team to beat.

“That’s something ‘Gats’ and the other coaches have drilled into us. We are not going to worry about any opposition. We know we have got quality in the squad.

“There is a lot of competition in that squad, and whoever goes on the field will give everything they’ve got for that jersey.”

Domachowski has already made a World Cup impression, leading the Wales players in a rendition of the Welsh hymn Calon Lan during the squad’s World Cup welcome ceremony in Versailles.

“As you can tell, I am a bit of a character, so ‘Nugget’ (team manager Martyn Williams) came up to me and asked me if I would lead it,” Domachowski added.

“So I said yes, and the boys were winding me up saying I could go on my own at first, but to be fair to ‘Gats’ he said we would all do it together.

“So I had to just lead it up, we had a couple of lessons and it went well.”