West Brom boss Alan Pardew questioned the use of VAR in their 3-2 win over Liverpool on Saturday, despite having benefitted from the system.
The Video Assistant Referee was called upon three times in the FA Cup fourth-round clash at Anfield, where the Baggies came from an early goal down to knock out the Reds.
The first instance saw Craig Dawson denied a goal for offside before the hosts were awarded a penalty and finally Joel Matip's own-goal was allowed to stand.
Pardew, though, feels there is too much mystery surrounding VAR, which is also slowing the game down, as evidenced by the decision to point to the spot following a foul on Mohamed Salah.
"It's hard to know where to start," the 56-year-old said. "You're all experienced reporters and have seen many, many games, but I don't think that's what you want to see going forward if you're a Liverpool fan or a West Brom fan.
"Firstly there's no communication from the referee to us. I haven't got the answers but as a football man on the sidelines I wasn't comfortable in that first half, it was kind of mysterious at times.
"It was four or five minutes, the Salah decision. You're going from high tempo work rate to nothing. We had a hamstring just after that. Now as a coach, we have to change, we're going to get our players to do a warm-up in that situation.
"The Dawson goal would never be disallowed in any game without the system (VAR). It's marginal, really marginal."
However, Pardew insisted Albion were worthy of a place in the fifth round of the famous cup competition, thanks to their fearless approach against Jurgen Klopp's side.
"It was a really professional, positive performance from us. We played without fear, which you have to do here. I set them up that way because after the Swansea loss I thought Jurgen would go very strong tonight.
"We've been very good without actually getting the three or four goals and tonight we looked like getting three or four goals and that's a really good sign. We're going to try and bring a striker in before Wednesday and that will hopefully lift us as well.
"I don't think Liverpool will have any complaints, I think we deserved to win. I'm very proud of the players and they should be proud of themselves."