Busquets, a three-time winner of the famous trophy, says that there are no positives to take from his side's third successive quarter-final exit and has apologised to supporters for the shock manner of this latest European setback.
"It's a very tough night, a sad night and one to forget," he told reporters. "We need to apologise to the fans for how we have fallen. This is the toughest blow I've received in the whole time I've been at Barca because of how it happened.
"I would be lying if I said we could use this as a learning experience because last year we went out in a similar way. Our results in Europe in the last two years have been very bad; we have to change things if we want to win the Champions League again."
Barca can still win a domestic double this term, as they are 11 points clear at the top of La Liga and also into the final of the Copa del Rey.