Watford assistant boss Zigor Aranalde said the referee had made a clear mistake in the build-up to Wrexham's added-time equaliser, resulting in a red card being shown to head coach Javi Gracia.
Ollie Rathbone's 92nd-minute goal denied The Hornets three points in north Wales on Saturday as the Championship game ended 2-2, but Aranalde said the game should have been stopped for a foul prior to the corner which led to it.
"Everyone could see the free-kick the referee didn't give leading to the second goal. It was a clear foul and he [Gracia] got mad for a couple of minutes and he decided to send him off," he told BBC Three Counties Radio.