The Leinster club-mates both start for the Lions a week out from the first Test against the All Blacks in Auckland but Sexton's fellow fly-half Farrell will be sidelined with a thigh strain, meaning his place on the bench will go to Dan Biggar.

The grade one quadriceps strain is considered mild although Lions assistant coach Steve Borthwick on Friday refused point blank to divulge any possible timeline for the Saracens and England star to return to action.

Borthwick's stonewalling during the Lions' only media interaction of the day in Rotorua did not do the tourists any favours, only leading to the supposition that Farrell must be a concern for that series opener with the world champions in eight days.

“He didn't train today, he's had a grade one muscle strain,” Borthwick said.

“The medical team take great care of him. Hopefully he'll be back on the field as soon as possible.

“When exactly it happened, I can't tell you. It was felt yesterday, dealt with immediately. Into recovery protocols straight away.”

When it was put to him that an accepted prognosis for a mild, grade one strain, was a seven to 10 days recovery time, the Lions coach replied: “I certainly don't go by that. I listen to our medical team who are far more qualified than I am.

“He'll be back as quickly as he's fit and able.”

As to the ramifications, if Farrell was forced to sit out the opening Test at Eden Park, Borthwick said: “You deal with hypothetical and I'll deal with what the facts are. He'll be back as soon as he's fit and able to be back.”

It's all about the speed of the ball...

Ben Te'o is primed and ready for #MABvBIL alongside Johnny Sexton#LionsNZ2017 pic.twitter.com/g14n8DtVUH

— British & Irish Lions (@lionsofficial) June 15, 2017

The Lions facing the Maori at Rotorua International Stadium on Saturday will press on with Sexton named to start at fly-half having been increasingly impressive in his three appearances on this tour to date t the extent that head coach Warren Gatland declared on Thursday that the series-winning playmaker for the 2013 Lions in Australia had got his “mojo” back following a lacklustre end to his Leinster season.

Yet openside flanker O'Brien thinks the increased focus on Sexton in Farrell's enforced absence will have no impact on the out-half's preparation for and performance against the Maori.

“You’ll get the normal Johnny,” O'Brien said. “Johnny is one of these guys who’s a perfectionist and that’s the way he’ll want it at the weekend and he knows that everything doesn’t go to plan, but he tries to get it there. He will prepare like he normally does for a game and he is excited about what’s ahead.

“It doesn't matter to him whether Owen's fit or not fit. Johnny's looking after himself first and foremost, getting his stuff sorted and his role within the environment right and that will help everyone else.”

As to the potential absence of Farrell, O'Brien added: “I don’t know if it will be a major blow to the squad. Obviously losing somebody to an injury and he’s not up for selection is obviously a blow for the wider picture but with the calibre of player we have within the environment _ you have Ben (Te’o), Jon Davies, you’ve Robbie (Henshaw), you’ve a lot of lads there who can cover that kind of 10/12 position, and Johnny obviously will be pulling the strings. So there’s other lads there to fill that void.

“Faz obviously has a lot of experience and has been playing very, very well, and he’s a good leader for us. He will be a loss obviously but with the quality of lads we have in someone else can fill that slot.”

Sexton's recovery from a poor performance in the Guinness Pro12 semi-final defeat to Scarlets last month and a disappointing first game on tour against the Provincial Barbarians was evident in the victory over Super League form side the Crusaders, when he came off the bench and played well alongside Farrell, who moved out to inside centre.

The fly-half is famously grumpy but O'Brien revealed he has found the perfect way to buck Sexton up.

“You give Johnny a bit of a cuddle sometimes and he perks back up, and gets his head back in the game. He’s a competitor, and someone who doesn’t like losing, and that can be tough. As someone said, he probably puts pressure on himself at times, but I wouldn’t have him any other way. I’d rather him barking and yapping at us, than not saying a word.

“Johnny was really sharp (against the Crusaders) and it was probably a difficult game to come into as well off the bench, but he was up to speed straight away. Yeah, he did look sharp and he was crisp again, and bossing us around like Johnny does. You know he’s on it when he’s giving out to you a lot.”