Finn Russell was the victim of what has been described as an "utterly senseless" incident in the Top 14 play-off match between Racing 92 and Stade Francais.
Stade Francais flanker Marcos Kremer was shown a red card just five minutes into the game for a reckless clearout. Remarkably, it was the Argentina international's third red card in 16 matches this season.
Russell left the field immediately for a HIA after taking a huge blow to the head as Kremer tried to clear him out of a ruck by ploughing his shoulder into his head.
Kremer was later pictured in the dressing room in tears.
The Scotland international returned to the field after passing tests and helped his team to a 33-20 win that puts them in the semi-finals.
Campaign group Progressive Rugby, who are demanding players, coaches and administrators work to make the game safer, said of the incident: "Utterly senseless. Every player that takes the field has a duty to play hard, give their all, to win.
"They also have a duty of care to their opposition, to not carry out recklessness acts that risk their opponent’s short or long term health."
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