The German made a late substitution to bring on back-up goalkeeper Kepa as the Carabao Cup Final approached penalties.
Edouard Mendy had been outstanding over 120 minutes, pulling off a host of key saves to deny Liverpool.
Kepa was then brought on because of his spot kick expertise but failed to save a single one of Liverpool’s 11 penalties before blazing his effort over the bar to see Jurgen Klopp’s side lift the trophy.
The decision to start with Mendy had actually been a surprise after the Senegal keeper had not played in any round leading up to the final.
But Tuchel insisted he stood by his call to bring on Kepa, just as he had in the European Sup Cup Final at the start of the season.
He said: “The players know and we did it before. But mistakes happen. I do mistakes. Edu did a big mistake and could have almost been punished with a decisive goal.
“If you want to blame someone, blame me. I take the decisions and I don’t take them to be the hero.
“We have reasons. I try to explain the reasons. It was not the first time and today it took 11 penalties to find a winner. There are no regrets. If you want to blame somebody, blame me, it is no problem.”
Chelsea’s players immediately surrounded Kepa to console him after his miss.
Tuchel added: “”It is harsh and we feel bad for him, but no blame. We took the decision like we did last time in a penalty shootout because Kepa is training with the players on a daily basis and they know how good he is. He has simply more time on the training ground to do this than Edou, who plays a lot more.
“Everyone knows how good he is, how difficult it is to shoot against him and this plays a huge part in how we shot today. Unfortunately, he couldn’t make a save – their penalties were brilliantly taken – and it was a bit harsh on him that he was the guy to miss the one and only penalty, but there is no blame.”