Bernard Jackman and Donal Lenihan pointed the finger at Gregor Townsend for the British and Irish Lions' lack of attacking spark and warned South Africa will run out comprehensive winners in Saturday's series decider unless Warren Gatland changes tact.

Lions out-half Dan Biggar passed the ball just three times during their thumping defeat by a resurgent Springboks last weekend, while the tourists’ only try in the two Tests came from a close-range driving maul.

Lions attack coach Townsend has come under increased scrutiny and Jackman warned this tour will be a 'black mark’ on his coaching CV should they again fail to fire in the third Test.

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The former Ireland hooker told the RTÉ Rugby Podcast: "It’s nearly impossible to see the Lions being able to beat the Boks at their own game, which they tried to do last week.

"I could see the thought process in that because they won the first Test without having to open up. The second half of the first Test was impressive and dominant but it was with Conor Murray and Owen Farrell playing pragmatic rugby.

"In Test two Gatland probably felt that’s the way to win the series. The problem now is the Boks have found their power game, they seem to be more match fit, and I don’t think the Lions can match them playing that way.

"Gatland has to gamble. Ali Price coming back in is a sign they want to play with more tempo, with Finn Russell on the bench. They’ve brought in Josh Adams and Liam Williams to solve their high ball issues but both have attacking prowess.

"The big question for me is whether the Lions can get the ball to the width. That’s nothing against Bundee Aki and Robbie Henshaw. Both of them are very good centres, but unfortunately on this tour we haven’t had a second playmaker, which you need to get around that rush defence.

Dan Biggar passed the ball three times during his 57 minutes on the pitch in the second Test

"We aren’t the first team to get caught by it and we won’t be the last, but we have been very conservative. For Biggar to only pass the ball three times in the second Test, and it’s not like we didn’t have any possession, we have become very one-out focused with a hell of a lot of kicking.

"Realistically, if we don’t change it’s going to be a comprehensive win for the Boks because I don’t think we can handle them at what they do.

"I really hope we do elaborate a little. If not this tour is going to be seen as a big black mark against Gregor Townsend’s attacking prowess."

Lenihan says the lack of an attacking plan is the biggest indictment of the series and questioned the Lions’ selection process.

While Warren Gatland has chopped and changed his backline, he has largely kept faith in the forwards, despite signs of fatigue during Saturday’s turgid second Test.

Former Lions lock Lenihan said: "Nine players will be starting their third Test, and five of those are in the second row and back row, who have been constant throughout the series.

"But we now have our third different centre combination, which shows they don’t know what their best combination is.

"They have reverted to two-thirds of the back three everybody felt should have been there from the first Test, but the bottom line is they don’t seem to have the capacity to challenge that drift defence.

"In terms of the rush defence and line speed South Africa play with, they defend narrowly so there is space out wide. You’d think they’d take that into consideration when putting an attacking plan together.

"But the bottom line is there hasn’t been an attacking plan. That is the biggest indictment of the series."

'Spingboks view Van der Merwe as a massive weakness'

Duhan van der Merwe is the only back three player to retain his place for Saturday's third Test

Liam Williams and Josh Adams have been drafted into the back three after the Lions’ struggles under the high ball last weekend, but Jackman and Lenihan both questioned the retention of Duhan van der Merwe on the left wing.

The Scotland international was sin-binned during the second Test for tripping Cheslin Kolbe, having been fortunate to escape punished for a late tackle on Pieter-Steph du Toit, and offered little attacking threat.

Jackman felt Anthony Watson was unfortunate to be dropped ahead of Van der Merwe and believes the South African is the wrong option against his native country.

"Speaking to some Springbok friends of mine, they see him as a massive weakness," said Jackman.

"He has ability going forward, he’s powerful, but power is the least important factor on the wing against the Boks. They don’t fear power. What they fear is real speed, cunning and footwork. I don’t think he’s the right weapon for this opposition.

"It’s a bizarre one and there’s huge pressure on his shoulders. It’s a difficult scenario for him given he wasn’t great last week and hasn’t huge experience at the top level – European finals, Grand Slam deciders, etc.

"Now he’s coming into a Test game to win a series, where he’s going to be targeted with high balls, which isn’t his strength. It’s a leap of faith from Townsend and Gatland."

Bundee Aki (right) partners Robbie Henshaw at centre this weekend

Lenihan believes the selection of Aki at centre should have allowed Gatland to opt for the likes of Louis Rees-Zammit or Watson on the wing instead of Van der Merwe.

"One of the reasons Van der Merwe was there earlier on in the series is because he’s so big," said Lenihan.

"Gatland was using him off the wing as the guy who was going to get the Lions over the gainline. Then you’re keeping Henshaw and Elliot Daly to play off that.

"But even now, Aki has been brought in because that’s one of the roles he’ll be expected to play. Why persevere with Van der Merwe?"

Jackman added Gatland and coaching ticket will be roundly criticised for their poor selections if they end up losing the series.

"The selection hasn’t made sense the whole tour," he said.

"Even not bringing someone like Henry Slade or Garry Ringrose. Let’s be honest, it’s highly unlikely they planned to play Elliot Daly at 13 in a Test match. It was the second time he played there in a Test match in the last five years.

"There have been lots of inconsistencies that, if we don’t win, will be used to point a finger at the coaching staff.

"The Springbok players responded to Rassie Erasmus and gave him a performance. Gatland needs the team to come out fighting for him this weekend because there’s a lot of areas where you could criticise them in terms of how they prepared."

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Follow South Africa v British and Irish Lions with our live blog on RTE.ie/sport and the RTE News app or listen to live commentary with Donal Lenihan and Michael Corcoran on RTÉ 2fm from 4.45pm on Saturday.