Pienaar admits that he still has a lot to learn but that the support he received from his team-mates made the transition easier than it otherwise may have been.
"It was my first game in the position but I think it went okay," said a modest Pienaar who produced an assured performance in both attack and defence.
"With Fourie (du Preez) at nine and Jean (de Villiers) outside me, it took a lot of pressure off me and that helped."
With neither World Cup winning fly-half Butch James or Tri Nations back up Peter Grant selected for the Boks' UK tour, Pienaar is expected to start against both Scotland and England on November 15 and 22 respectively.
If the 24-year-old displays the same mental toughness, distribution skills, attacking instincts and accuracy with the boot both out of hand and at goal, Lions supporters could well being seeing Pienaar line up against the tourists in Durban, Pretoria and Johannesburg next summer.
"I knew the responsibility so there was stuff I had to work on in the week and try and improve on. Obviously, I had to work hard on that," added Pienaar.
"It was a bit different and I need to work a bit more on my decision making but I'm just happy that the guys pulled the game through. It was good challenge playing against brilliant players. They had good attacking backs and it was a good test for us.
"You're a bit more exposed than you are at nine but I tried not to be too nervous. I knew it would be a big stadium and the Welsh are passionate supporters but it was just brilliant to play at such a great venue, and luckily the goal kicking went well. The roof helped a bit so I can't complain about that!"