It is the Lions’ final game before their first Test showdown with world champions South Africa in Durban next Saturday.

And despite the opening Springboks clash looming ever closer, Lions head coach Ian McGeechan insists nothing will be decided in terms of his Test team until he draws it up on Wednesday.

It means O’Callaghan and company have gained just the incentive they require for a match the Lions should win comfortably and claim their sixth successive tour victory.

The Lions will take 24 players to Port Elizabeth, with the remainder of their squad heading for Durban tomorrow.

Among those looking to leave a final impression on McGeechan will be O’Callaghan, his fellow lock Nathan Hines, who starts at blindside flanker, prop Andrew Sheridan and wing Shane Williams.

Scrum-half Mike Blair, meanwhile, faces a late fitness test on a foot injury. If he is ruled out, Harry Ellis can expect promotion off the bench, with Williams providing number nine cover.

“This is a great position for everyone going out tomorrow,” said O’Callaghan, who becomes the fourth skipper on tour after Paul O’Connell, Brian O’Driscoll and Phil Vickery.

“It is a chance to force the coach’s hands with a huge performance, and that’s a great way for everyone to feel

“This is the biggest honour of my life, I was taken aback when ’Geech’ told me. It’s huge.

“You must enjoy moments like this when you are living out your dreams. There is a tremendous buzz around the squad.

“I think this tour has pushed a lot of us out of our comfort zones. It’s been great, a bit old school, and something a lot of us really haven’t had.”

Some players, the likes of O’Connell, O’Driscoll, try machine Tommy Bowe, full-back Lee Byrne and scrum-half Mike Phillips, are Test certainties.

But McGeechan reiterated his stance that all fit players remain in the frame.

“I told the players that on the first day, and I won’t change. We won’t pick the Test team until Wednesday morning,” he said.

As for moving Hines to six, McGeechan added: “We’ve played Nathan there before. With Joe Worsley covering seven, for us it’s a logical decision to play him (Hines) at six.”

There is also an opportunity for in-form James Hook, the Lions’ late match-winner against Western Province at Newlands two days ago.

He wears the number 10 shirt, and McGeechan said: “James has been brilliant.

“He’s trained very well, and he’s playing with a lot of focus. He’s done everything asked of him, he’s been very good in what he has done.”

McGeechan also paid tribute to O’Callaghan, who has reached a career pinnacle at the age of 30 following 55 Ireland caps.

“I got to know Donncha pretty well in 2005 (Lions tour of New Zealand), and I know his reaction when he was first selected. He’s a fantastic tourist.

“I valued what he did in 2005 when I was working pretty closely with him, and he has taken it a step forward with this group. You don’t have to have led a lot to know people will follow you.

“I value what he has brought. I didn’t know him before 2005, and our relationship has grown on this tour. He’s very deserving of the captaincy, in my book.”

The Southern Kings will play their first-ever fixture tomorrow, with coach Alan Solomons drafting in a handful of players with Guinness Premiership appearance, including former Harlequins centre De Wet Barry and former Bath backs Wylie Human and Frikkie Welsh.

Whether the game ends up having much bearing on McGeechan’s Test selection remains to be seen, but there is a fierce determination to get another job done and preserve their 100% tour record.

“I’ve felt we have had to use all six games, and hopefully out of that comes the way we want to play,” McGeechan continued.

“If I tried to do it any other way, I wouldn’t have been honest or fair.

“The way the players have taken it on board, I couldn’t have asked for anything more. We know we have got keep that focus.

“I’ve tried not to hide anything – I am not going to say one thing, and do another.”

The Springboks, meanwhile, have drafted Cheetahs flanker Heinrich Brussow into their squad preparing in Durban for Saturday’s Test.

Brussow, who had an outstanding game against the Lions nine days ago, has been summoned amid continuing doubts surrounding Schalk Burger’s fitness.

Burger is nursing a calf muscle injury, and is racing against time to be fit for the opening Lions encounter.

Brussow said: “I was disappointed to miss out on selection into the original squad, which has a lot of great players, but I am very happy about being called in.

“It will be great to be part of the squad and the Lions series, and I am going to grab my chances with both hands.”