Simone Inzaghi was left "very angry" after Inter had a third goal chalked off before conceding a late equaliser against Monza in their 2-2 draw on Saturday.
After Matteo Darmian's early opener was pegged back by Patrick Ciurria, Lautaro Martinez seized upon a Pablo Mari error to put Inter back ahead and seemingly on course for victory.
But with the score 2-1, referee Juan Luca Sacchi blew for a foul as a free-kick was swung into the Monza box, which Francesco Acerbi nodded in, for a contentious Roberto Gagliardini push.
With a goal that likely would have killed the game off ruled out, Inter suffered late heartbreak as Luca Caldirola scored in the 93rd minute to snatch a point for Raffaele Palladino's side and deny the Nerazzurri a fourth straight Serie A victory.
Inzaghi was fuming after the match, believing the referee's early whistle cost his side all three points as they missed the chance to move within five points of leaders Napoli, ahead of the Partenopei's visit to Sampdoria on Sunday.
"I'm very angry at what I saw," Inzaghi told reporters. "Unfortunately, after five years of VAR, there was an error that penalised us.
"A clear mistake on Acerbi's goal, there are two Monza players who fell between them. It's a huge disappointment on our part.
"I complimented Palladino, [but] without that mistake we would have won the match."
Romelu Lukaku impressed for Inter as they ended Napoli's unbeaten start to the season on Wednesday, but Inzaghi opted to start Martinez alongside Edin Dzeko up top against Monza, over the Belgium international.
With Lukaku struggling for fitness, Inzaghi is unsure when the striker will be back to his best, saying: "Time will tell, he's training in the best possible way.
"He had a very good first half with Napoli, today it was difficult. We'll do the analysis tomorrow when we'll be more rested."
Asked whether he felt Inter sat back too much late in the game, inviting Monza on, Inzaghi replied: "In the first half we conceded little or nothing.
"There are always difficult opponents, Monza are organised and have excellent players.
"Without what we've seen [Acerbi's disallowed goal], there wouldn't have been this question.
"Now we start again. It's normal that there is huge disappointment on everyone's part."
