Johnny Sexton will realise a boyhood dream when he captains Ireland for the first time in Thursday's World Cup clash with Russia.

The 34-year-old British and Irish Lions fly-half will take the armband with Ireland making 11 changes to face the Russians, resting the likes of World Cup skipper Rory Best.

Sexton is fit again after a bang to the thigh that kept him out of Sunday's 19-12 defeat by hosts Japan, and revealed his pride and excitement at being handed the honour of leading his country.

"It's a massive honour; I spoke to Joe Schmidt this morning so I only found out myself over the last few hours," said Sexton.

"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 in or around trying to get there.

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

"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.

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

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

Sexton toughed out Ireland's fine 27-3 win over Scotland that set them rolling from the off in Pool A.

The 85-cap Ireland playmaker had to cede kicking duties to Conor Murray due to that bang to the thigh against Scotland, and then that same niggle forced him out of the Brave Blossoms loss.

Now, though, he insists he is fully fit – and ready to kick goals against Russia.

Asked if he is 100 per cent fit again, Sexton said: "Yes, I kicked a little bit yesterday.

"Then I kicked again today in both sessions so I feel good to go now."

Ireland's clash against Russia will be played out under the Kobe Misaki Stadium's closed roof.

Scotland's 34-0 victory over Samoa in the same ground on Monday proved a hugely humid affair, with condensation causing all sorts of handling issues for both teams.

Sexton admitted Ireland must be on their guard and adapt their game accordingly, to cope with the unusual conditions.

"We watched the game last night and we watched the England game there as well," said Sexton.

"When it's an indoor stadium you think air con and whatever and it will be a bit cooler, but it's quite the opposite from what we hear.

"So it's something we're going to have to be mindful of but even when you play outside the ball gets quite slippery, the boys said it got that way against Japan, especially in the second-half.

"The longer the game went on the sweatier everything got and the ball ended up like a bar of soap.

"So it's something we have to be conscious of, we've got to go out and play smartly, but hopefully it won't make too much impact."