Hansi Flick lauded Barcelona's mentality in their "unbelievable" 5-4 comeback victory over Benfica in the Champions League on Tuesday. 

The result sealed their place in the last 16, but they had to pull off a monumental turnaround after Vangelis Pavlidis' hat-trick had the Blaugrana 3-1 down at the break.

Raphinha reduced the deficit just after the hour to give Barcelona hope, but Ronald Araujo's own-goal four minutes later seemingly put the result beyond the visitors. 

However, Robert Lewandowski, who scored a penalty in the first half, scored his second spot-kick 12 minutes from time, a goal that kickstarted the dramatic turnaround.

Eric Garcia then levelled the contest before Raphinha notched his brace in the sixth minute of second-half stoppage time to seal a huge three points for Flick's side. 

"It was a very crazy game. The most positive thing was the mentality we had. We came back and that's wonderful. That's football and that's why we love it," Flick said. 

"I don't think I've ever experienced a comeback like this. It is unbelievable. We didn't play so well in the first half. They are very good and scored first.

"They made us defend very deep. We were not in the right position. In the second half we were better and substitutions helped us a lot."

The clash at the Estadio da Luz was the first in Champions League history to finish 5-4, with Barcelona becoming just the second side in the competition’s history to win a game despite conceding four or more goals (Borussia Dortmund 8-4 Legia Warsaw in November 2016).

Wojciech Szczesny's display was also placed under the microscope after the match after making errors that led to two of Benfica's goals in the opening 45 minutes.

Szczesny first came out to claim a long punt forward and clattered into Alejandro Balde, allowing Pavlidis to gather the ball and roll into an empty net. 

The Polish goalkeeper then fouled Kerem Akturkoglu inside the box after rushing off his line, with Pavlidis completing his hat-trick from the resulting penalty. 

However, Flick defended Szczesny, insisting that the 34-year-old improved after the break and arguably kept his side in the contest. 

"Which player does not make mistakes? It is normal. Szczesny had some mistakes, but all the players made mistakes in the first half," Flick said.

"We win together, we lose together. We are a team. I liked what I saw in the second half, he saved a clear chance for Benfica."

Despite the adulation of the victory, Flick urged his players to turn their attention to their next LaLiga clash, which comes against Valencia at the Camp Nou on Sunday. 

Barcelona drew 1-1 with Getafe in their last league fixture, leaving them third in the standings and seven points behind rivals Real Madrid at the summit. 

"The victories give us time to keep believing in this project and send the message to the young players that we can and want to improve," he said.

"It's very important to focus on the Valencia game and we also want to beat Atalanta. We don't have to think that we are at ease."