Paris Saint-Germain head coach Thomas Tuchel described Tuesday's 2-1 loss against Manchester United as one of the club's worst games, the German particularly scathing of the first-half performance in their Champions League opener.
PSG succumbed to Marcus Rashford's strike with three minutes remaining in Paris, where last season's Champions League runners-up made a losing start in Group H.
Ligue 1 holders PSG were without Marquinhos and Marco Verratti and United took advantage – Bruno Fernandes converting a 23rd-minute penalty, though Red Devils forward Anthony Martial netted an own goal 10 minutes into the second half.
But United left the French capital with maximum points thanks to Rashford's late winner, condemning PSG to a first home defeat in the Champions League group stage in 25 games.
"In the first half, we were simply not on the pitch," Tuchel told beIN SPORTS. "It was not our level.
"I don't know why, but I can just say that it was not our level, in moving the ball, in possession, in counter-attacking, in challenges, in intensity.
"By far, one of our worst games, one of our worst first halves."
"The good news was that it could not be worse. Okay, we were down 1-0, it is easy to play better in the second half and we had to step up, it was clear," Tuchel added after star forward Neymar failed to score in four consecutive Champions League appearances for the first time since November 2013.
"We tried to do some tactical changes because of the injury of Idrissa Gueye, we tried to bring on one more offensive guy, which was a risk that we paid for at the end also. It was like this today.
"From the start until the end it felt like we were never at our highest level, and we weren't really into the match like was absolutely necessary on this level."
When asked about the atmosphere behind closed doors, Tuchel said: "I don't feel it. We've played how many games in the Champions League now without supporters? I don't feel it, sorry."
PSG, however, have the chance to respond when they travel to Group H opponents Istanbul Basaksehir next week after hosting Dijon in Ligue 1 on Saturday.
But Tuchel said: "We have a lot of injured players, a lot of quality that is missing and for that I am not sure if this is good, no."