In the first quarter of Saturday's game at Marvel Stadium, which the Saints won by 82 points, Mansell shoved O'Connell into the path of Richmond forward Tom Lynch and St Kilda's Anthony Caminiti.
When attacking the ball, Lynch unintentionally collided with O'Connell, leaving the concussed Irishman dazed and confused, and unable to continue playing.
The match review officer graded the incident careless conduct, severe impact and high contact, slapping Mansell with a three-game ban.
Tuesday night's hearing looms as a landmark case, after the AFL recently issued a memo to clubs warning them of the dangers of recklessly pushing other players.
In Mansell's defence, the Tigers appear almost certain to reference West Coast's Reuben Ginbey escaping scot-free in the pre-season for pushing Richmond's Sam Lalor into a contest.
That caused the prized No.1 draft pick to suffer a broken jaw and concussion.
Tigers coach Adem Yze made sure to reference that incident when asked about Mansell's push.
"Based on previous incidents, I don't think that has been an issue," Yze said.
"So hopefully ours isn't either.
"We had Sammy Lalor break his jaw, if it is a similar incident, so it's pretty hard to change the rules during the season."
Mansell is currently set to miss games against Brisbane, Fremantle and Gold Coast.
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