Lewis was charging back with the flight of the ball in round three as Western Bulldogs defender Jarrod Harbrow was moving at full speed towards it in the opposite direction, and when Harbrow flew to spoil, his hip crashed into the Hawk's head.
The 23-year-old was unconscious before he hit the ground, although he returned later in the game and played the following week.
He had a couple of down games following the incident, and was initially dropped for last weekend's clash with the West Coast Eagles, although he was reprieved when gun forward Lance Franklin missed with injury.
Lewis admitted he might not have been quite right in the weeks following the hit.
"At the time you do all the tests and you think everything's okay, but when you're actually out on the field and you're at that high-intensity, you probably lack a bit of decision-making at the right time," he said on Monday at the Hawks base at Waverley Park.
"So it probably hindered my game for a couple of weeks, and looking back, whether or not I should have played, I don't know."
The AFL employs world's best practice procedures in the management and treatment of concussion - players are put through a battery of neuro-psychological tests at the start of each season to establish a baseline against which they can be measured if medical staff suspect a concussive episode has occurred.
This allows medical staff to determine if the player is impaired in any way due to the injury, and an informed decision can then be made about letting the player back onto the ground during that match or if he is fit to play in following weeks.
Lewis said he had done all the required testing and been fine, although a short break between matches hadn't helped.
"It's a computer-based test, which is decision-making, but the reason why it was hard was because we had a six-day break so we couldn't get out on the track and train at high intensity," Lewis said.
"If we had a longer break we may have had that chance, but it's basically just computer testing, remembering cards and stuff like that."
