Joe Schmidt says Ireland have received feedback from World Rugby that three offside penalties awarded against them in the Japan game were incorrect calls.

Ireland fell to a 19-12 defeat by the tournament hosts in their World Cup Pool A clash in Shizuoka.

"It's pretty hard to keep getting off the line when you are getting those calls," said Ireland coach Schmidt.

"Two of them were from an assistant referee who is going to be refereeing us on Thursday."

Schmidt added: "So we know we're going to have to be on our best behaviour."

The coach bemoaned referee Angus Gardner's penalty count after Ireland squandered a 12-3 lead against Japan, who are now on the brink of a first-ever World Cup quarter-final appearance.

However, with the prospect of Thursday's must-win game against Russia looming, Schmidt claimed Saturday's shock result was "fantastic for the tournament".

"Everywhere we've gone, the Japanese people have been incredibly excited about the game," he said.

"It's great for our pool if you're an independent observer because it's thrown the pool wide open and everyone's chasing Japan in our pool now."

Despite the setback against Japan, Schmidt says Ireland will maintain focus on their "performance-orientated goals" as they look to get their World Cup campaign back on track with victory over Russia under the roof at the Kobe Misaki Stadium.

"For us, we can't put anything on the scoreboard without getting the things we need to put in place; that we build the pressure or that we create the opportunities from," said Schmidt.

"I felt the first 20 minutes last weekend were very good - we got the right field position and turned a few balls over which was frustrating.

"But we converted two tries on the back of some really good line breaks and maybe that was to our detriment because we stepped back after that and didn't play with the same front foot.

"You can't afford to do that against a quality opposition."

Ireland captaincy a massive honour - Sexton

Schmidt has made 11 changes for the Russia game, one of which sees fit-again fly-half Johnny Sexton return and captain the side for the first time.

Sexton, 34, missed the defeat by Japan with a thigh problem, but says he is fit and ready to lead Ireland into Thursday's clash.

"It's a massive honour," said the current World Rugby Player of the Year.

"I spoke to Joe this morning so I only found out myself over the last few hours.

"So I haven't even had a chance yet to tell my family or anything, but I'm sure they're going to be very proud as well.

"It's something that I've thought about since I was a kid; it's something that I've made a lot of decisions around trying to get there.

"It's taken a while but it was worth the wait and I'm incredibly proud."

While wearing the captain's armband represents another achievement in Sexton's career, he insists it won't be a significant change given his senior standing in the team.

"I want to be captain now of a good performance and a good win in a World Cup game so that's my focus now," he added.

"I don't think anything changes really for me.

"I have a big responsibility in the team for me anyway, so nothing's changed."