In the incident, during the second quarter of the Hawks' 55-point win over Collingwood at the MCG, Hodge slid in to win a ground ball while O'Brien held his feet.
The Hawthorn skipper crashed into O'Brien's legs with his head, winning a free kick and seeing the Magpies defender placed on report.
Lewis said players had been taught that the player who kept his feet should win the free kick, meaning he would await the MRP's verdict on Monday afternoon with interest.
"The way it's been explained to us is, if you slide in and contact someone front on in the legs, it is a free kick to the guy who is standing over the ball," Lewis said on Monday.
"That's what we've been told.
"It will be good to see the outcome today, because it will give us more clarification on what the rule actually is.
"The umpires may have made a mistake, we don't know.
"From what we've been told, we can only try and keep our feet and not slide in as much, and not put ourselves in the position to give away a free kick."
On Sunday, Collingwood coach Nathan Buckley said the incident and the way it was assessed would act as a "test case" for the rule in the future.
The rule, which forbids players from making forceful front-on contact below an opponent's knees, was introduced this season in a bid to eradicate serious leg injuries, such as that suffered by Sydney Swans forward Gary Rohan last year after he was collected by a sliding Lindsay Thomas.
Lewis said players had been trying to adjust their games to accommodate the new rule, but it was particularly difficult in wet conditions such as those at the MCG on Sunday.
"It's hard in wet weather football, when it's slippery and you need to dive on the ball, to stop the opponent from kicking it off the ground or doing something like that," he said.
"You definitely think about it when there is a ground ball, what your options are."
Hawks players were given the morning off after the big win, the club's second in succession against highly rated opposition.
Lewis said the team was pleased it had been able to run away with the game after Collingwood had the better of play early.
"The first half was really tough in terms of adapting to the conditions," the midfielder said.
"They probably adapted a bit better than we did, and it took us until half-time to establish the way we wanted to move the ball.
"In the second half we controlled the ball a lot better, we were a lot cleaner with our hands, and we were able to put scoreboard pressure on."
