Presnel Kimpembe may have been guilty of "overconfidence" with the mistake that preceded a tense finale in Paris Saint-Germain's 2-1 victory over Nantes on Tuesday, said Thomas Tuchel.
Mauro Icardi's first-half goal was added to by Thilo Kehrer to put PSG in control of the Ligue 1 game at La Beaujoire, on a night when the Parisians were without Neymar due to a rib injury.
However, Kimpembe's attempt to flick a pass from Marco Verratti behind his standing leg and to Kehrer ended up going straight to Moses Simon, who raced through to score with 22 minutes remaining.
Simon missed a one-on-one with Keylor Navas and substitute Renaud Emond wasted a glorious chance to snatch a point for Nantes in stoppage time.
"Sometimes it's like that. The pitch was difficult and I am impressed with the way we played for 70 minutes," Tuchel told Canal+.
"It was excellent. We were aggressive and we had total control. We could have made 4-0 and after one mistake, it was 2-1.
"It may be overconfidence, but it can happen. You shouldn't take too many risks. They had opportunities and played with great courage afterwards.
"It's football. But the most important thing is that we had quality, and we always had opportunities to score the third. But the mentality is excellent."
Kylian Mbappe started despite reacting angrily to being substituted during Saturday's 5-0 victory over Montpellier at the Parc des Princes.
The World Cup winner was bright in the first half but missed a couple of chances as PSG came under pressure in the closing stages.
Asked for his assessment of Mbappe's display, Tuchel said: "He played a top match."
Kehrer was frustrated PSG were unable to find a third goal but refused to lay blame on Kimpembe for the pressure they came under.
"In the second half, we had big chances, but we didn't score and we didn't kill the match. We knew that Nantes play well at home and remain aggressive. They pushed and it was not easy," said Kehrer.
"I don't think [Kimpembe's mistake] made us doubtful. We felt like we were always in control. In matches, there are always mistakes. We are a team and we are here to win."