Unai Emery feels the referee made the difference in Paris Saint-Germain's 0-0 draw with Montpellier by not awarding what he saw as a "clear" penalty.
Edinson Cavani was sent tumbling inside the box by Pedro Mendes - already on a yellow card - with 10 minutes left but official Clement Turpin signalled for play to continue.
Montpellier defender Mendes did not appear to make contact with the ball and Emery was unsure how the foul was missed.
He told a post-match news conference: "The penalty is very clear. The referee made the difference on it. It was clear on the pitch and on the television pictures, too."
The PSG boss commended Montpellier's defensive efforts as they held firm to end his side's 100 per cent start to the Ligue 1 season.
Neymar was absent due to a reported knee injury and Emery believed the team could have pushed harder for a breakthrough in the absence of the Brazil star.
1 - Paris have only registered 1 shot on target v Montpellier (Mbappé), their lowest tally in a L1 game since August 2016 v Monaco. Mute. pic.twitter.com/edjU0YZ6iM-- OptaJean (@OptaJean) September 23, 2017
"The merit belongs to our opponents, who defended well, closing the spaces with great efficiency," said the PSG boss.
"We played the game as we wanted, with a significant amount of possession, but we need to push more to score goals. We had opportunities, but that's not enough to win games.
"The main goal is to win and today it is true that one point is not enough. This game leaves us a lot to analyse to continue our progress."
Despite the disappointment, Emery tried to look for positives in the result.
He added: "It's not a good result but I'm glad the team remained calm about looking for spaces to score - I think it's a sign of progress.
"Analysing afterwards is always easier, but it's true on the pitch we had to attack the space more. When we did that, we had better opportunities."