New South Wales Blues and Penrith Panthers lock forward Isaah Yeo has revealed he doesn't believe he was concussed during the opening tackle of State of Origin 1 on Wednesday evening in Sydney.

The veteran lock, in attempting to make a tackle on Queensland prop Josh Papalii to start the game, reeled out of the tackle and appeared to stumble back into the line.

He was cleared by Blues' doctor Nathan Gibbs on field, and the independent doctor in the NRL's bunker found no reason to bring Yeo out of the game despite seemingly to clearly show concussion symptons.

Talking after the game, Yeo said he doesn't believe he was ever concussed and remembers the entire incident.

“It was obviously a big one on Papalii there, but I felt fine,” Yeo said.

“I remember everything, I’ve been knocked out and it definitely wasn’t that. I just lost a bit of balance.”

Yeo said he was worried about being taken out of the game.

“When you’re knocked out, you don’t remember anything and I remember absolutely everything. I remember the play [making contact with] the wrong shoulder, all of that sort of thing. It was all good.

“The head feels fine, no stress.”

NSW doctor Nathan Gibbs told The Daily Telegraph that he was never shown footage of Yeo stumbling, only of the initial incident, and the independent doctor reportedly referred to it as Category 3, which leaves it up to the team medical staff.

“I still haven’t seen that. They show us what they choose to show us," Gibbs told the publication.

“The bunker doctor is controlling that. It is their call – not ours. That is how the system works well. We’re not concerned about that aspect of it.

“The people who have all the camera angles can make a better call. In the end, they make the call.

“At ground level it is hard to see because people are in your line of sight."

The NRL's head of football Graham Annesley said that an investigation would be kicked off by the NRL, although added that every game is reviewed from a HIA point of view.

“We review all HIA’s every week as a matter of procedure,” NRL head of football Graham Annesley said.

“Last night will be no different.”