The runaway Ligue 1 leaders, well on course for a sixth title in seven seasons, lost 2-1 at home to bottom club Guingamp after the Brittany side converted two late penalties in the League Cup match.
“We lost a game, but most of all an opportunity to win a trophy,” said Tuchel.
Having failed to make an impact on the Champions League in recent years, PSG used to compensate with domestic titles, lifting the French Cup every year from 2015-18 and the League Cup from 2014-18.
PSG were in the driving seat after Neymar’s header put them ahead in the 63rd minute, only for the visitors to claim a shock victory.
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“Actually, we played with too much self-confidence during the whole game,” Tuchel added. “We thought nothing could happen to us.”
The elimination, PSG’s first domestic cup defeat since January, 2014, will at least lighten the club’s schedule before they travel to Manchester United next month for their Champions League last-16 first-leg game.
“We have to bounce back because we are PSG, a great club,” German Tuchel said.
PSG travel to Amiens as Ligue 1 action resumes on Saturday.
(Reporting by Julian Pretot, Editing by Ed Osmond)
