The world champions need to win one more game to avenge their series defeat by the British & Irish Lions 12 years ago, while Paul O'Connell's men need to win to keep the series alive.
"The first Test was always going to be important to both teams. Now both teams are really fighting - one to finish and one to survive so the pressure will be twice as big next weekend," said Smit.
"We were pretty rusty and the intensity wasn't what I would have liked. But these 80 minutes will have helped us for the next one and if we can improve our concentration we will be back in business again."
Smit admitted that all the talk about the power of the Lions scrum in the build-up to the first Test made his team concentrate on that area.
Extra training sessions against the Emerging Springboks forwards got Smit's pack ready for their big challenge and they came out and gained a significant first-half advantage over the Lions in that area.
"All the talk in the build-up to the game was about the scrummage. It was an era we worked a lot on," said Smit.
"There have been a lot of sessions before the game and a lot of talk. All the build up and talk about it meant we did our home work.
"But the Lions won't lie down and they will come back twice as strong after this. They will know our scrum and drive went well so they will try to counteract that which means we will have to be even more accurate.
"There was some rustiness involved in our game. There wasn't concentration for the full 80 minutes and our kicking game went down the toilet.
"The Lions are a serious team and they took advantage of any territory we gave them. We will have to work on our concentration next week."
Smit was replaced after 65 minutes with his team leading by 19 points, but Springbok coach Peter de Villiers was forced to send his skipper back on for the final few minutes as the Lions went in for the kill.
"I was quite happy to get back on and to steady the ship again. We all know the waves were coming in from the Lions side," admitted Smit.
"The key moment was the line-out we disrupted at the end through Guthro Steenkamp. We just had to get our hands on the ball having given it away so often in the second half."