Wojciech Szczesny promised his best is still to come after starring in 10-man Barcelona's 1-0 Champions League round of 16 first-leg win against Benfica in Lisbon on Wednesday.

Raphinha scored the only goal of the night as Barça recovered from Pau Cubarsí's 22nd-minute red card to give themselves a slender advantage heading into next week's return game.

The victory was built on a fine performance from goalkeeper Szczesny, who made eight saves to earn his eighth clean sheet in 14 games since replacing Iñaki Peña in the starting lineup.

"It is still to come, don't worry," Szczesny told reporters when asked if it had been his best match since coming out of retirement to sign for Barça last October.

Szczęsny's form has steadily improved since he came into the team in January.

Wednesday's display at the Estádio da Luz from the former Juventus and Arsenal stopper was a huge improvement on how he performed when the two teams met in January in the league phase of the competition.

On that occasion, as Barça came from behind to win 5-4, he was at fault for one of the Benfica goals and also gave away a penalty.

This time, he made a string of fine saves, but it was one from Kerem Aktürkoğlu in the first minute which he was particularly proud of.

"I really liked the first save," he added. "We came here a few weeks ago and they scored early, so it was really important to start the game without conceding."

Despite Szczesny's heroics, UEFA's player of the match award was given to Pedri, although the Barça midfielder said he would give it to the former Poland international.

"He deserves it, he stopped everything," Pedri said.

"Pedri got the trophy, but I think I could take half of it home," Szczesny joked in response.

There was some skepticism when Barça coach Hansi Flick decided to replace Peña with Szczesny while Marc-André ter Stegen is out injured, but that call has been justified in recent weeks.

"I think this is very important when you have a clean sheet, with 10 players only, that you have a great and fantastic goalkeeper on the pitch," Flick said in his post-game news conference.

"Today was a great performance from him and he saved us to get the clean sheet. Very good. I am very happy for him and also for the team.

"I think with every match he has more confidence. I know he can play on this level because we see him every day in training and he's a fantastic goalkeeper."

The odds looked stacked against Barça when Cubarsí was sent off halfway through the first half for a last-man challenge outside the box.

However, despite having a player less for well over an hour, they defended stoically while remaining a threat on the break, with Raphinha snatching the winner in the 61st-minute with a strike from outside the box.

It was the Brazilian's ninth goal in as many games in this season's Champions League, with Flick going on to describe his pride at how his players dug in.

"The reaction [to the red card] was really good," the Barça coach added. "I am really proud of the team, they defend really good. They manage the game really good and such a match, for nearly 100 minutes, is not easy to handle.

"I said to the players 'Chapeau.' After the 22nd minute, with 10 players, it was not easy. This is a big win. But we know we also have to play the next match and Benfica are a good team. We have to take care about that."

The second leg takes place back in Barcelona at the Olympic Stadium next Tuesday, with the winners advancing to a quarterfinal against either Borussia Dortmund or Lille.