Andre Onana has acknowledged he made a "really big mistake" in Ajax's 1-1 draw with Benfica in Group E of the Champions League.

Ajax goalkeeper Onana gifted Benfica an opener in the 29th minute of Wednesday's encounter in Lisbon, putting the visitors' defence under pressure with an unnecessary Cruyff Turn before failing to deal with the resulting throw-in, enabling Jonas to tuck home.

However, with Dusan Tadic having equalised just after the hour, Onana atoned for his calamity, pulling off two brilliant saves to deny Rafa Silva and Gabriel.

And Onana insists that Erik ten Hag's side were always confident of fighting back.

"I made a really big mistake. I made the wrong choices, twice, which led to their goal," Onana told UEFA.com.

"But as a goalkeeper you just have to be strong and look forward.

"Even though it wasn't our best game, I still thought we were better than Benfica.

"We kept faith, because we have great strikers so there was always belief that we could score."

Ajax defender Matthijs de Ligt echoed Onana's sentiments, adding that the team did not lose faith in their goalkeeper despite the error.

"We didn't give Onana a hard time during the break, because we're all in this together and support each other," the teenager told UEFA.com.

"And let's not forget that he has made fantastic saves during the qualifiers and in the group phase already.

"Benfica had a last chance, so when Onana saved it, it was like scoring a goal. We need to improve and keep fighting. Hopefully we'll win the next game and go through."

Ajax will qualify for the last 16 should they beat AEK Athens, while a point would be enough unless Benfica claim an unlikely victory against group leaders Bayern Munich.

Benfica defender Alex Grimaldo, though, is hopeful of keeping the dream of progressing alive.

"What was missing is what has been missing in our past matches: scoring goals," Grimaldo told UEFA.com.

"We failed to score the second, we conceded a goal in an accidental play from them, we didn't have any luck.

"We are four points behind Ajax and there are six points still to play for. We can do it and we'll play until the end."