Joe Schmidt has backed Luke Fitzgerald to challenge Robbie Henshaw for Ireland's inside centre starting berth.
Head coach Schmidt hailed Leinster's utility back Fitzgerald for slotting seamlessly into Ireland's 12 shirt for the 50-7 rout of Canada.
Ireland eased past Canada in Cardiff to take early control of Pool D on Saturday, with Schmidt afterwards tipping Fitzgerald to compete for a regular midfield role.
Henshaw missed Ireland's World Cup opener with hamstring trouble but could recover in time for next Sunday's Romania clash, though Darren Cave may slot in at 12 as Schmidt rotates his squad.
"Darren Cave plays 12 or 13 and that's a real advantage for us," said Schmidt.
"But we always intended giving Luke a chance at 12, because he's played 13 and 11 in the build-up, and we wanted to build our versatility.
"Darren's pretty likely to have an involvement next week, and that will allow us to mix and match a little bit as we have done through the build-up period.
"But at the same time we know we've got to get results and we've got to go after them right from the start.
"We need to have people that we can put out there who can do the job, and we have confidence in our full squad of 31.
"With Luke, Keith Earls, with Darren Cave and Robbie, and Jared Payne and then also Ian Madigan at 12, there is a bit of scope for flexibility and an ability to maybe change up the way we're playing the game depending on who we're using."
Cave was a surprise inclusion in Ireland's final World Cup squad, the Ulsterman selected ahead of a third scrum-half in Schmidt's calculated risk.
Schmidt's decision to select Fitzgerald out of position at 12 ahead of a natural inside centre raised eyebrows then, but Ireland's Kiwi boss insists he needs to use all his resources over the World Cup's pool stages.
"I thought Luke did really well at 12, his distribution to give Dave Kearney space for his try was great," said Schmidt.
"Defensively he was sound and his ball-carrying is a strength.
"He punched a half-gap off a scrum and that put them under pressure straight away.
"He stays alive really well in the defensive line, he's got good alertness, communicates really well and slotted in well."
Canada captain Jamie Cudmore's cheap yellow card gifted Ireland total control at the Millennium Stadium, and Schmidt's men refused to release their choke-hold for the duration.
Sean O'Brien, Iain Henderson, Johnny Sexton and Dave Kearney crossed to secure the try bonus point in just 35 minutes, before Sean Cronin, Rob Kearney and Jared Payne completed the rout.
Ireland captain Paul O'Connell was sin-binned for an unwitting but ultimately cynical offside, both teams' totems slipping off the disciplinary tightrope though remarkably without a punch in sight.
Fly-half Sexton hit back to top form after lacklustre showings in warm-up defeats to Wales and England, passing 500 Test points against Canada and drawing high praise from Schmidt.
"He'll reflect on the game and the first wide pass he made which looped into touch," said Schmidt.
"It was the perfect opportunity, it was the right decision but he didn't quite affect it accurately enough.
"So, he'll probably chastise himself for that in amongst about 30 other really positive involvements.
"That's the way he's driven and I think that's the way he drives the team which is a real bonus as well.
"I felt we built our way into the game pretty well. I think we showed a fair bit of respect for Canada.
I think Canada showed why they deserved that respect. They're a very combative side.
"For us to build our way into the game and successfully put a few phases together effectively to build that scoreboard pressure on them as well was satisfying."