Monaco stunned PSG with a 3-2 win overnight, bringing the team up to second position on the Ligue 1 table. A disappointing set back for the Parisians who face a crucial Champions League tie against RB Leipzig next week.
Cesc Fabregas scored a late winner from the penalty spot as Monaco came from two goals down to stun reigning champions Paris Saint-Germain 3-2 in Ligue 1 at the Stade Louis II on Friday.
Kylian Mbappe had netted a first-half brace, including a penalty, against his former side, leaving his current team seemingly on course for a ninth consecutive league win.
But German international Kevin Volland struck twice for Monaco after the break and Fabregas converted from 12 yards in the 84th minute after Abdou Diallo had been sent off for conceding the all-important penalty.
Without their French international striker Wissam Ben Yedder after he tested positive for coronavirus, it was a long way back for Monaco but they reduced the deficit seven minutes after half-time when Gelson Martins set up Volland to score from close in.
"I am more surprised than I am angry," said Tuchel, who was also disappointed to see further first-half goals for Mbappe and Moise Kean disallowed.
"I saw two totally different halves. First of all we completely controlled the game...and then the second half was completely different. I can only say it is our responsibility."
Niko Kovac's Monaco climb up to second in the table, four points behind PSG, but Lille can reclaim second spot and move to within two points of the leaders if they beat Lorient on Sunday.
"If you come back from two down to win 3-2 it is for sure something special, but I don't want to glorify it too much," said ex-Bayern Munich coach Kovac.
"We cannot stop and say everything is done. It was a big victory but nothing more."
Neymar on the bench
PSG have been severely handicapped by injuries and suspensions this season, and Neymar was only deemed fit enough for a place on the bench at kick-off after missing Brazil's World Cup qualifiers over the last week due to fitness problems.
Mbappe was back in the starting line-up, however, after missing his club's last two outings prior to the international break with a hamstring injury.
His ninth goal of the season leaves him just one away from a century of goals in a PSG shirt since his arrival from Monaco at the start of 2017/18 in a 180 million-euro deal. He even had another goal disallowed just before half-time.
Meanwhile - Rennes warmed up for their Champions League rematch with Chelsea in the worst possible fashion on Friday, going down to a 1-0 home defeat at the hands of Bordeaux in Ligue 1.
The Brittany side were beaten 3-0 by Chelsea at Stamford Bridge in their last Champions League outing earlier this month.
They slip to fourth in the Ligue 1 table, behind third-placed Marseille on goal difference and six points behind leaders Paris Saint-Germain.