Manchester United boss Louis van Gaal has been warned about his future conduct for his comments after last month's goalless draw with Cambridge United in the FA Cup.
Van Gaal told the BBC's Match of the Day that "every aspect" was against his side, including the referee.
The Football Association decided his comments breached rules, but Van Gaal has escaped a fine.
United went on to beat the League Two side 3-0 in the replay at Old Trafford.
Van Gaal, who subsequently repeated the accusation, contested the FA charge, which said his words had "alleged and/or implied bias on the part of the match referee and/or brought the game into disrepute".
United now face a home quarter-final clash with Premier League rivals Arsenal as they seek to win a trophy in Van Gaal's first season in charge.