Although the Wearsiders dominated during the first half in Leiria, the Black Cats fell behind to the second tier Portuguese side 37 minutes in when Volnei Feltes smashed a stunning strike from distance into the top corner.

The visitors continued to push, enjoying a series of chances before Jules Ahoka levelled with a header in the 67th minute from Nordi Mukiele’s delivery. Noah Sadiki then struck in stoppage time to clinch three points.

Victory is Sunderland’s second in the competition having beaten AZ Alkmaar in their opening match.

The Black Cats’ attention quickly turns to a Premier League clash against Bournemouth on Sunday and they return to European action next Thursday with a trip to Lech Poznan.

Reflecting on the game, Le Bris told Sunderland’s club media channel: “Back in Europe, 53 years later, in Portugal especially, and winning this game just at the end is really special.

“It’s a symbol I think and important for many reasons, the first one is for the club and our fans, they were fantastic once again.

“Also we are growing up and we need experiences. I think the team showed this evening this belief until the end, which is really important for us. We showed again that we were in this mindset.”

With the score level at 1-1, the Black Cats went close again through Ahoka and Chris Rigg before Sadiki had the final say at the death.

The midfielder’s goal was his first for Sunderland since arriving at the club last summer and Le Bris believes it can be a “starting point” for him.

“That’s important for him to step up, to add this layer in his game because he has the ability to dribble, to shoot, to make key passes,” the Black Cats boss added.

“Now it’s the next layer, so it’s a starting point I hope.”

Sadiki found the winner in the third additional minute of the game when Granit Xhaka flicked the ball into his path and he hit a brilliant half-volley past Lucas Paes to claim three points.

The midfielder revealed skipper Xhaka had encouraged him to shoot and expressed his delight at opening his account with the club.

“I can’t really explain it, it’s something big that happened my first goal for the club. I was waiting for it, fighting for it,” Sadiki told Sunderland’s media channels.

“When (Xhaka) touched it, I heard him scream ‘shoot’. I didn’t think twice I just shot and hoped it was going in and that the keeper wouldn’t save it. It went in and I’m really happy.”