But O’Sullivan believes O’Connor’s mobility around the pitch – he has been preferred to the bulkier Eric Miller at openside – could help restore the balance as Ireland target only their second victory against South Africa.

“Johnny deserves selection. He’s had a very good start to the season. He’s good at the breakdown and a fine link player. He works well on the ground and there will be a fair bit of work to do there,” he said.

“He was in the mix last year but he’s been very much on the radar this season. Once we picked him in the 22 it was a question of whether we wanted to go with a big back row or one with an openside.

“The South African back row is big and physical. It will be a challenge for us physically and we’ve decided to go for an out-and-out openside for that reason. Maybe we’ll have an advantage in certain areas with Jonny in the team.”

Ireland’s previous lack of interest in O’Connor led to speculation the 24-year-old would opt to represent England when he became eligible for the world champions on residency grounds.

But the Galway-born forward – who makes up the back row alongside Simon Easterby and Anthony Foley – has been rewarded after striking a rich vein of form for Wasps so far this season.

His path into the side has been aided by injuries to Keith Gleeson and Kieron Dawson but his position as a standout openside would have warranted his inclusion anyway.

O’Connor said: “I’m delighted about the news. I didn’t know about it until today and now I will try keep everything low key and concentrate on the game.

“Things have been getting better for me with Wasps. I struggled a bit at the start of the season but the last four or five games have gone well for me.”

In total O’Sullivan has made three changes from the side beaten 26-17 by South Africa in Cape Town during the summer with Geordan Murphy and Denis Hickie joining O’Connor in the starting line-up.

The groin injury suffered by Gordon D’Arcy – the star of this year’s RBS 6 Nations – has forced a reshuffle with Shane Horgan switching to centre where he will partner skipper Brian O’Driscoll.

Murphy returns to the right wing while Hickie takes the number 11 shirt in his first international appearance for nearly a year following the ruptured Achilles tendon he sustained on World Cup duty.

O’Sullivan said: “Obviously with Gordon D’Arcy injured centre came under discussion. Shane was going to play alongside Brian for the second Test in South Africa but Geordan was hit by a chest infection so we didn’t get to use that combination.

“But we will go with it now in the absence of Gordon. Shane has operated at centre alongside Brian quite a bit for Leinster. He’s played most of his rugby for Ireland on the wing but I think he has the qualities of an inside centre.

“It will be interesting to see how he and Brian work together – it’s a different chemistry which has worked with Leinster and I’m confident it will work for us.”

On his day, Murphy is one of the most dangerous runners in the game and O’Sullivan believes he will see the greatest return from the gifted Leicester back by giving him a license to roam.

“I wouldn’t be too fussed about the number on Geordan’s back. The game goes through many phases now so he might appear on the wing or at full-back, depending on the situation,” he said.

“It’s one of those areas where you can swap quietly and quickly. He’s in the back three and that’s the main thing.”