Grimsby boss Michael Jolley felt aggrieved by the early dismissal of Andrew Fox in Saturday's 1-0 FA Cup third-round defeat by Crystal Palace.
Fox was shown a red card in the second minute for a studs-up tackle on Andros Townsend that referee Martin Atkinson viewed as a booking before the VAR intervened, resulting in a red card.
Grimsby defended valiantly against their Premier League opponents and held out until the 87th minute when Jordan Ayew nodded in the winner, by which point Palace had produced 30 attempts on goal.
"I only saw it live – I haven't had a chance to see it again since the game finished," Jolley said.
"The thing I would say is that it was an FA Cup tie and it was the first challenge that had been made in the game.
"The pitch had been watered before the game and it may have been over-exuberance on Andrew's part because he's not a malicious player.
"So we feel slightly harshly done to, particularly on the basis the referee gave a yellow card initially. We don't get VAR in League Two and it punished us in the end.
"Our players were tremendous. To lose a player so early in the game made it extremely difficult.
"We already came here as massive underdogs because we were without four centre halves. For the players to get so close to a positive result was testament to their efforts."
Palace boss Roy Hodgson was happy to take Atkinson's original decision to award a yellow card, but claimed the incident is evidence that the VAR system works.
"Martin is an excellent referee who referred very well," Hodgson said.
"There were no complaints from us at the yellow card when we were stood so far away, we just accepted his decision.
"He then took the advice of VAR, doing what a good referee does, because that's what VAR is there for.
"He did say to me before the game that VAR comes into play for possible red cards."
Hodgson admitted it was a poor spectacle at Selhurst Park but praised the defiance shown by Grimsby.
"It was a war of attrition. Football matches to be exciting need a cut and thrust," Hodgson said.
"When it is purely a matter of us having the ball for the entire game and facing a team who are very well organised, it doesn't make for a good game.
"Grimsby deserve credit, they made life very difficult for us. They regrouped and showed some very good individual defending.
"We were doing our best to break through and our players deserve credit for keeping going. It took us a long while but we got there in the end."
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