Mauricio Pochettino was left "frustrated and disappointed" after Paris Saint-Germain failed to register a shot on target in Sunday's shock 2-0 loss to Rennes.
The Ligue 1 leaders' eight-game winning streak to begin their league campaign came to an end at Roazhon Park as goals from Gaetan Laborde and Flavien Tait proved decisive.
PSG registered 13 shots but failed to test opposition goalkeeper Alfred Gomis from any of those, with Kylian Mbappe having a second-half strike ruled out by VAR for offside.
Mbappe had earlier scuffed a shot over the crossbar with only Gomis to beat, while Neymar was way off target with a volleyed attempt six yards out with the scores still level.
Pochettino also started with fellow superstar forward Lionel Messi, who had a game-high five shots, the most notable of which saw him hit the crossbar from a free-kick.
Angel Di Maria was brought into the side in place of Ander Herrera from Tuesday's 2-0 win over Manchester City, but Pochettino has no regrets over his attack-minded selection.
"I don't think we can look at our system. We played 25 of our best minutes of the season [in the first half]," Pochettino said at his post-match news conference.
"We didn't start the game well, but we then had 25 or 30 minutes of good quality football. It was a shame not to capitalise.
"We then had two psychological blows, conceding just before and just after half-time. The match was then open. We created chances but had a hard time.
"Rennes grew in confidence and we started to become frustrated."
The defeat was Messi's first since joining PSG from Barcelona in August, the Argentina international still without a goal in three Ligue 1 matches.
Mbappe, meanwhile, has now had 17 shots since last finding the net in Ligue 1.
While Messi, Mbappe and Di Maria played the full 90 minutes, Neymar was withdrawn 14 minutes from time after managing just that one wayward attempt in the first half.
Rather than point the finger at individuals, however, Pochettino accepted the blame for his side's first league loss since early April, a run of 15 matches.
"When we won against Man City, it was down to a collective effort," he said. "The first person in charge is me. What we did for 25 minutes was of very high quality.
"We must extend that to 90 minutes. I am satisfied with one sector – we created a lot of situations and opportunities."
PSG's 13 attempts without registering a shot on target is their highest in a Ligue 1 match since Opta started collecting such data in 2006-07.
Rather than put the rare setback down to fatigue on the back of a tough European match with Man City five days ago, Pochettino accepts a lack of cutting edge was to blame.
Asked if he was feeling angry, Pochettino said: "Yes, a bit. Nobody likes to lose games. We can't underestimate what Rennes did, but we are frustrated and disappointed.
"We had chances to score and then conceded a couple of goals. Situations like this leave us bitter and disappointed.
"But it's not to do with playing in midweek. We've had five days since then. I repeat, we played 30 minutes of good football today.
"We had control of the game and conceded when on top. We were immediately 2-0 down in the second half and then it's a different game."