Lopeti Timani has been banned for four weeks after kicking Rory Arnold in the head during Rebels' 19-17 Super Rugby win over Brumbies on Saturday.
The back row was shown a yellow card following the incident in the first half of the Melbourne side's first victory of the season.
Timani was cited and accepted a guilty plea, so the beleaguered Rebels will be without the Australia number eight for a month.
Foul Play Review Committee chairman Nigel Hampton QC ruled: "Having conducted a detailed review of all the available evidence, including all camera angles and additional evidence, including from the player and submissions from his legal representative, Michele Williams, the Foul Play Review Committee amended the citing to Law 10.4(m) Any other acts (not previously referred to) which are contrary to good sportsmanship.
"With respect to sanction the Foul Play Review Committee deemed the act of foul play, which involved an intentional, but glancing, strike to an opponent's head by the Player's leg, merited a mid-range entry point of eight weeks.
"However, taking into account mitigating factors including the player's excellent Judicial record, his on-field apology to the opposing player, his remorse and his early guilty plea, the Foul Play Review Committee reduced the suspension to four weeks.
Timani will miss the clashes with Sharks, Southern Kings, Lions and Reds.