Advice from Paul O'Connell, cramming for the French game and proving the doubters wrong - Jonathan Sexton has reflected on his journey back to the field of play as he looks to lead Ireland to a crucial Cardiff victory under the Friday night lights.

The 31-year-old out-half was plunged into an Aviva pressure cooker having spent a month on the sidelines when the French rolled into town two weeks ago.

When the chips were down, he delivered.

The Leinster playmaker starred in a fine home win, but though he seemed to take his first appearance since hobbling out of the Champions Cup game against Castres in January in his stride, Sexton has revealed how much of an ask it was, with the wisdom of an old friend required to help him through.

"The French game, it was like cramming for a big exam," he told RTÉ Sport's Michael Corcoran ahead of the Principality Stadium showdown (8.05pm).

"I was on the pitch on the Tuesday for the first time with the lads. In the back of your mind you're wondering whether you calf is going to be right.

I feel like my body is in a much better place now. Time will tell.

"I was trying to get as much in the system as possible on the Tuesday, Thursday and Friday.

"You always try to take the positives out of a bad situation. I gave Paulie a ring, who would have had a period in his career where he struggled with injury a bit and then he had the end of his career where he really had a great run at it.

"He gave me great advice about who to go to, and how to manage myself.

"The match-fitness will probably be a bigger issue this week playing Wales. They try and keep the ball in play as long as possible. They back their fitness. It's going to be a bigger challenge for me."

Sexton had been there before.

In 2015 Joe Schmidt threw him into a bruising clash against France after he'd spent three months out with a concussion. He was named man of the match in an 18-11 victory. 

Overcoming adversity is all part of the game, he says.

"Obviously it was a very frustrating few weeks, having to sit and watch after doing so much hard work in that block before Christmas to get myself right," he said. 

"I felt I was coming into good form in those European games. I put myself under pressure to play in that Castres game, to get myself match-fit and get myself sharp before the Six Nations and I paid the price, playing with a dead leg really.

I've been written off in many areas of my play.

"A lot of people have played with it and got away with it. I just didn't. It was really disappointing and, I suppose, lesson learnt. 

"There were times last season when it wasn't good enough to be coming off in games with soft-tissue things. I feel like my body is in a much better place now. Time will tell. Hopefully I can turn the corner.

"I've had so many setbacks in my career; I've been written off in many areas of my play. This is just another challenge to overcome."

The roof will be closed tonight; the Welsh, stung by heavy criticism after their loss to Scotland, will be spitting fire.  

Cool heads and committed bodies will be needed to escape with the right result. Sexton is ready for battle.

"I've always backed myself - not in an arrogant way or an over-confident way - but I've always had a belief that I could contribute to the team in a positive way," he said. 

"I hope I get to do that over the next few years. 

"I know they're wounded, they're a very proud nation and a proud bunch of players and they'll come out firing. We need to match that. 

"It's a special stadium. You're so close to the supporters. I haven't played on a Friday night over there but I'm sure people going to the pub a little bit earlier will make for an even more special atmosphere. The guys are really excited about it, but we know the cauldron we're going into and how tough it's going to be. 

"To win the championship we've got to beat France, Wales and England over consecutive weekends. It's a huge challenge for us."

Live Six Nations coverage of Wales v Ireland on RTÉ Two and RTÉ Player from 7pm on Friday (KO 8.05pm), live radio commentary on RTÉ Radio 1 from 7.45pm and live blog on RTÉ.ie and the RTÉ News Now app.

Live coverage of Wales v Ireland (KO 11.30am) in the Women’s Six Nations on RTÉ Two and RTÉ Player from 11.15am on Saturday.

Live Six Nations coverage of Italy v France (KO 1.30pm) and England v Scotland (KO 4pm) on RTÉ Two and RTÉ Player from 1.20pm on Saturday.

Live coverage of Wales v Ireland in the Under-20 Six Nations on RTÉ Two from 6.15pm (KO 6.30pm) on Saturday.