Mike Phillips believes the Lions can again out-run the Springboks in the final quarter of Saturday's second Test and level the series in Pretoria.
The Wales scrum-half scored a third try for the tourists five minutes from time in the first Test to spark a frantic late assault that came up just short.
"We worked hard on conditioning before we came here and seven games in, we are very fit and very strong," he said.
"The last 20 minutes [in the first Test] we came on really strong."
After trailing 26-7 early in the second half in Durban, the Lions dominated the final half-hour after rectifying the scrummaging problems that had cost them dear early on.
Despite facing the Springboks at the home of the Super 14 champions the Bulls, who supply five of the hosts' side, Phillips believes the Lions have nothing to fear and should feel confident.
"We are a quality outfit, the support we have received out here has been outstanding, and we want to put the same massive effort in again and get the win to keep this series going," said the Ospreys half-back.
BRYN PALMER'S BLOG
"We are all very excited we have got the opportunity and are desperate to put things right. We had problems in some areas last week but in open field and with ball in hand, we were far better, we had great fitness and it was a great battle to the end.
"If we had lost by 40 points then we might be worried but we played all the rugby. We have to be confident and believe in ourselves and I think we can do it."
Physical conditioning coach Paul Stridgeon told BBC Sport earlier this week that the Lions always thought their fitness would come to the fore in the final quarter.
"We weren't surprised, we thought that with our pattern of play we would tire them out after 60 minutes, and that was the time we would start to dominate," he said.
"The boys have worked hard, are in good shape and have a good feeling going into this game. If we keep with the same approach, we can do the same again."
The Lions travel to Pretoria on Friday, the eve of the game, to lessen the effects of dealing with the extra altitude, with Pretoria at 4,173ft (1,271m) above sea level.
Flanker David Wallace, one of seven Irish players in the starting XV, a post-War record, also believes the Lions have an edge in fitness that could prove vital if they can live with the Springboks for the first hour.
"I think we have got to believe that," he said. "Even during the game when we got into a pattern, we felt we were doing damage and starting to create space. I think we have got to back ourselves there.
"We have just got to look at it as a one-off game. What has happened before, and what happens afterwards, doesn't matter. Hopefully if things go well and we win, the momentum is then with us for the final Test."
Fellow Irishman Rob Kearney, promoted to the starting XV after replacing the injured Lee Byrne in the first Test, accepts Saturday will be pivotal to whether these Lions create their own piece of history or continue a depressing trend of series defeats.
"When you are in the 22 it is great to be on the bench but it is never quite the same," he said. "Being part of the first XV is fantastic and what we do on Saturday will determine whether we stand out as Lions and what we will be remembered for.
"We have to make sure we start off the way we finished last week. We proved in the second half we have the potential to beat the Springboks. It is important for us to do that from the word go."