Brentford midfielder Yehor Yarmolyuk was sent off for “violent conduct” towards Liverpool defender Jeremy Jacquet in the box.
But Liverpool did not receive a penalty because it took place while the players were waiting for a corner to be delivered and the ball was not in play.
The incident occured in first-half stoppage time and as Brentford led Liverpool 1-0 thanks to Lewis Keane-Potter’s earlier header.
But the hosts were reduced to 10 men after Jacquet went down in the box holding his face and referee John Brooks was sent to the pitch-side monitor by the VAR.
After watching replays of the incident, Brooks decided that Yarmolyuk had committed a butting action when he bumped into Jacquet and moved his head towards the Frenchman.
A similar incident took place last week at Old Trafford when Rodrigo Bentancur moved his head towards Luke Shaw’s face and the Tottenham midfielder was also sent off.
Brooks announced on the pitch that Yarmolyuk had been sent off for a “headbutt action” but that it would remain a Liverpool corner.
The incident was the second VAR intervention of the match after Brooks awarded Liverpool a penalty, only to overturn his decision at the pitch-side monitor.
Meanwhile, Dominik Szoboszlai’s return from injury lasted just 32 minutes as the influential midfielder was forced off after for what appeared to be a recurrence of the issue.