Chelsea manager Thomas Tuchel has revealed he was left in a "dark place" after Manchester United knocked Paris Saint Germain out of the Champions League during his time in charge of the French club.
Tuchel has a chance to avenge that painful loss against United when Ole Gunnar Solskjaer's side visits Stamford Bridge in a crucial Premier League clash on Sunday.
That will be the fifth time in just over two years that Tuchel has faced United.
The 47-year-old still has the mental scars from PSG's 2019 meltdown against United.
After a 2-0 victory at Old Trafford, PSG were left stunned at Parc des Princes three weeks later when they conceded a penalty in stoppage-time to suffer a 3-1 defeat and exit the last 16 on away goals.
"I can be very honest, after that match I was two days in a very dark place and I can tell you I was not able to speak to anybody and to think about anything else than this defeat," Tuchel said.
"That maybe was the worst defeat that I experienced because it came from nowhere. It was, in a way, in the circumstances that it arrived. I was for two days in a dark place for a coach to be at."
It remains the only time the former Borussia Dortmund boss has felt that low after a result but he admitted it proved a crucial learning experience.
PSG were able to bounce back and win the Ligue 1 title before Tuchel led them to a Champions League final defeat against Bayern Munich last season.
"I didn't experience anything like this ever again or before," Tuchel said.
"It was in the circumstances, this game, how we arrived there, the pressure around the club concerning the round of 16, the history before and the result of the first match and the way the second match went with the VAR decision in the last minute.
"It was like it came from absolutely nowhere and that's why this hit was hard to take. But, like I said, I was two days in a dark place but then we gave the players two days off and I think that was the best for everybody.
"After that, it's like this in sports, it can teach you that you have to stand up and accept that a defeat is sometimes necessary to grow and develop and to ask yourself decisive questions.
"That can hurt and the reward was one year later, it was almost the perfect reward when we arrived in the final and we came a long way for that. It was through adversity and it's often said that it makes you stronger."
Chelsea, unbeaten since Tuchel replaced the sacked Frank Lampard in January, must beat United to keep in touch in the top four race, while the visitors need a win to maintain their faint hopes of catching leaders Manchester City.