Maurizio Sarri accused English officials of not knowing how to use VAR after his team's 1-0 EFL Cup semi-final defeat to Tottenham, while Spurs boss Mauricio Pochettino is also not a fan of the system in its current guise.
Harry Kane gave Tottenham a slender advantage to take into the second leg at Stamford Bridge in two weeks' time after he dispatched a 26th-minute penalty.
The England captain was brought down by Chelsea goalkeeper Kepa Arrizabalaga, but only after the linesman had flagged for offside.
The referee consulted his video assistant, whose pictures showed Kane to be level with Cesar Azpilicueta, and proceeded to book Kepa and award the spot-kick.
Sarri told Sky Sports that Chelsea's own images suggested the Tottenham striker was offside, although his main complaint concerned the early offside flag as he argued that stopped his defenders from retrieving the situation.
"I saw a few minutes ago the video from our camera. It was offside," the former Napoli boss said.
"Our camera was in line with Kane and it was offside. But it's not important.
"It was really important for the man [assistant referee] to follow the ball. It [the offside flag] did not help our defenders.
"I don't think English referees are ready to use the system.
"If you are not sure with this system you have to follow the ball and then at the end of the action you have to decide. On this occasion, he stopped."
As such, Sarri is apprehensive over the proposed full-scale introduction of VAR in the Premier League from next season, having observed teething problems in his homeland.
"They have to study this system because in Italy the first period was very difficult," he added.
"It is very strange that in the Premier League they don't have the system and in the Carabao Cup there is the system."
Despite being the beneficiary of the game's major talking point, Pochettino sounded a similarly cautionary tone to Sarri – the ex-Espanyol boss having not enjoyed what he has seen from VAR in La Liga.
"I don't like, I don't like," he told Sky Sports. "Today we get the benefit but watching another league like La Liga, no one is happy.
"For me the benefit is nice but I am not happy doing it like this.
"I prefer the technology but in a different way – being clear about how we are going to use it.
"I am pro-technology, you cannot stop evolution. But waiting how we wait for the benefit like this…
"I think it is not clear how we use the rules. The photos we use, we have to be clear how we use them."
Pochettino added: "I am watching La Liga every week and no one is happy – the big clubs or the small clubs. That is a good example for us."
"We still have six months to improve that system."