It is unacceptable and must not happen, says Aberdeen's Swedish coach Jimmy Thelin.
Aberdeen lost 1-2 away to Dundee United and thus also lost fourth place to Dundee in the Scottish top league.
After the final whistle, home supporters entered the pitch and some of them taunted the visiting Aberdeen fans. A chair was thrown from the away section in response, but it hit the team's defender Jack MacKenzie, who was never substituted in the match, in the head.
We must now get all the facts on the table about what actually happened. All we know is that Jack suffered a serious injury when he as a player was just doing his job. This kind of thing must not happen, says Jimmy Thelin.
Celtic had already secured the league title in Scotland.
