The Portuguese calls for calm despite being "not happy" at the Champions League loss, which came six years to the day after the final game of his first spell at Stamford Bridge
Despite struggling for fluency, the hosts looked set to emerge victorious courtesy of Oscar's 45th-minute strike but late goals from Mohamed Salah and Marco Streller turned the game on its head, condemning the Blues to a first home defeat in the group stage since October 2003.
The result came six years to the day after a 1-1 draw with Rosenborg that represented the final game of his previous spell in charge of the club but, despite suggesting that his team lacks maturity, the Portuguese was relaxed after the game.
"Of course we are not happy but football, in easy moments, is good fun and easy for everybody," Mourinho told Sky Sports. "In the difficult moments is when you see the man and the character and the personality.
"In the bad moments, I want everyone to keep calm and let me be responsible. I'm not in shock because I know football is a game and the reality is that sometimes you don't win.
"I'm not happy, of course, with the result but I think [Basel] played well. They scored the equalizer in our best moment and, after that, we were punished at a corner where we are strong and work hard."
England defender Gary Cahill believes that Chelsea paid the price for not raising its game after Oscar's opener.
"I think, in the first half, we were in control," he added. "We went in 1-0 up and had good control of the game. We knew we could go up a level but we didn't do that and that's what has cost us. We didn't quite step it up and paid a price."