But the Ulster Academy player showed little sign of nerves as he booted four penalties as part of a handsome contribution to the province's 17-16 defeat of the Welshmen at Ravenhill.
Having accepted his man of the match award and drawn breath after a thrilling game, O'Connor said: "Obviously I am delighted. We needed to win, we talked about it all week. It was important to get the league campaign off to a winning start. We achieved that, so that is the most important thing.
"We were after the points and a good performance. The forwards put in a huge performance and we came away with what we wanted."
Describing it as "every boy's dream to play at Ravenhill and kick the winning penalty for Ulster", the former Ireland Under-20 international said he "just went through the same routine" for his match-winning penalty kick right at the death.
"I was quite nervous before the game to be quite honest. But that early successful penalty gave me a lot of confidence. I had said if I got the chance I would have a crack at goal, and get the feel for it. It was nice to get settled in early," he explained.
"Playing in front of a big crowd like that added to the nerves. But the fans were terrific and it was a pleasure for me to play in front of them."
O'Connor thanked Ulster boss Mark McCall for giving him the chance to start such a big game, given that the experienced Adam Larkin was also available to him.
"It was a big decision for Mark to throw me in and it was a massive risk, but he showed great confidence in me. I'm just glad I could repay his faith and to come away with the win was great."