DURBAN, South Africa (AFP) - The British and Irish Lions are ready to counter fire with fire in the opening Test against South Africa here on Saturday, according to assistant coach Warren Gatland.

Gatland said he expected a hugely physical encounter at the Absa Stadium, and compared the game to chess "with collisions".

"We've got to play some rugby," the New-Zealand-born Wales coach said. "We've got to defend and be confident in our own defence that we can go through phases without the ball.

"Physically winning those collisions in defence will be important for us.

"On attack you're trying to create quick ball and get on the front foot, and defensively you're trying to give the opposition slow ball and stop them getting on the front foot.

"It's a bit like a game of chess," he said. "And who does dominate in those collisions and the breakdowns will determine the outcome of this series."

The Lions are seeking a first series win in 12 years, the last coming against the Springboks when they were also world champions, having won on home soil in 1995.

And Gatland admitted that the task now facing the Lions was similarly daunting.

"South Africa are the best team in the world at the moment. They're world champions and went through the autumn series last year undefeated," he said.

"They're a very settled side and have a lot of experience and a huge amount of caps."

The Kiwi acknowledged that head coach Ian McGeechan had plumped for a mobile pack of forwards to work their Bok opposition around the ground.

"If we get involved in a set-piece battle, and a real physical one-on-one confrontation game that's something that the South Africans are very good at and will enjoy," he said.

"We have gone for mobility. Hopefully, we'll move their pack around a bit, play through lots of phases and ask questions of their tight five."

The team chosen for Saturday includes many of the players who featured in what Gatland dubbed "our two best performances", against the Golden Lions and the Sharks - which the Lions won 74-10 and 39-3, scoring 15 tries to two.

"A lot of the combinations that performed really well (in those games) are playing," he said, adding that the Lions management were "looking for clarity and consistency" from New Zealand referee Bryce Lawrence on the breakdown.

Gatland said that there was less respect for the breakdown during experimental law changes because an infringement only meant a free-kick, which importantly ruled out a kick at goal.

Now the old rules have been reinstated which make a breakdown infringement punishable by a penalty and the Lions have suffered in varying interpretations from referees on this tour.

"The referee wants both teams to be positive at the breakdown," he said.

But Gatland was confident and said that the Lions could take heart from France's shock 27-22 win over New Zealand last week to spring a surprise on the Springboks, who have been seven months without a Test match, and for whom many key players have not enjoyed game time for five or six weeks.

"Traditionally in the first Test, you do have an opportunity to catch the home team underdone," he said.

"We've got six games under our belt and a lot of training sessions, so we'll go into this game full of confidence and self-belief.

"We have to go out there and impose our game on them as much as possible. Our scrum has been very good and dominant in all games that we've played.

"We have a lineout that can deliver us good ball and in terms of mobility of the forward pack we think we can get around the park and we've got some players in the backline that get us across the advantage line."