Barcelona coach Ernesto Valverde felt his team took a "step forward", but he lamented their 0-0 draw with Olympiacos in the Champions League.
The LaLiga leaders failed to score in a Champions League group-stage match for the first time since 2012 as they were held in Greece on Tuesday.
Despite the result, Barcelona retained a three-point lead atop Group D after Juventus drew with Sporting CP.
Valverde praised his players for their efforts despite not getting the result they wanted.
"We were lacking a goal. We tried to get closer to their area on the basis of longer possession," he said.
"But they did a great job in defence and tried to hit us on the counter-attack, spurred on by their fans.
"You could see what amazing people there are here. We wanted to secure qualification but we failed.
"It was still a step forward, but not the one we wanted. The players emptied their tanks out there."
Barcelona fail to score in a group stage match for the first time since December 2012. October 31, 2017
The clash marked a return to his former club for Valverde, who coached Olympiacos in two stints in 2008-09 and 2010-12.
Despite being on the opposite side of the fanatical Olympiacos support, Valverde praised the fans.
"The answer to everything is how well our opponents played. They stuck tight together as a unit. We were up against an opponent that did their job well from start to finish," he said.
"I always had this atmosphere in my favour and today it was against me. I know what the Champions League means to these fans because I've experienced it myself many times.
"It may have come as a surprise to people coming from Barcelona, even though everyone knows how intense Greek football support can be. It was extraordinary. Really nice."
