Eddie Howe suggested referees have become too reliant on VAR after the technology was conspicuous by its absence in Newcastle United's 3-1 FA Cup win at Aston Villa.
Sandro Tonali netted twice and Nick Woltemade rounded off the scoring as Newcastle fought back in the second half of Saturday's match at Villa Park, having trailed at half-time.
Tammy Abraham's first goal since returning to Villa opened the scoring, but a straight red card for goalkeeper Marco Bizot immediately before the interval shifted the momentum in Newcastle's favour.
While Bizot's red card was clear-cut after he raced off his line to scythe down Jacob Murphy, several other contentious calls from Chris Kavanagh went against Newcastle.
Abraham was clearly offside for the Villa goal, but VAR is not in operation until the fifth round of the FA Cup and so the on-field decision to allow the goal stood.
Lucas Digne, meanwhile, was fortunate to escape a red card in the first half and was somehow not penalised for a handball in his own area in the second period.
Asked about those decisions after the game, Howe said: "Obviously, we've got the benefit of replays on the bench, and you can see what's right and what's wrong, and we agreed in that first period that every decision was going against us.
"The officials don't make any decision on purpose, it's just what they think at the time, but without VAR, I thought there were a lot of errors today.
"Once the decision is made and it seems like there is no way back, there's nothing you can do. You've got to move on quite quickly, although all through that half, it seemed like I was debating a referee decision.
"That's not me, I don't do that, but I felt there were so many going against us. Today, it makes sense why VAR is necessary. To help the referees."
Asked if officials were now overly reliant on technology, Howe said: "I think there's an argument to say yes.
"Because when VAR's there, there's always a sense of, 'Well, I won't give that, but let's check it.' I think then your decision-making maybe isn't as sharp as it may normally have to be, so maybe there's a difference there.
"I'm always torn on VAR. That emotion, that joy that you get in that moment, I still really love, and VAR takes it away. But then, on the other side, I was wishing there was VAR on the first goal against us and probably throughout that game."
Villa boss Unai Emery admitted Bizot's dismissal was the turning point in the game, but after making several changes to his lineup, the Spaniard still saw some positive signs.
"The players competed fantastically, but after we had the red card it became more difficult in the second half," Emery said.
"We tried but it was not enough. Newcastle is a really fantastic team, and they are contenders in this competition. I think we must analyse this match and feel like we're improving.
"Today, we're not happy, but I saw some things in the squad that can help us for the future in the Europa League and the Premier League."