"To be good defensively is one step to get results and we have nine points. We are basically I think one point away from qualifying and one victory away from winning the group so we are fine."

He said United had discussed how to put pressure on the young goalkeeper at set-pieces, including putting players around him on corners to chip away at his confidence.

Mourinho made four changes to the team that started Saturday's cagey 0-0 draw with Liverpool in the Premier League, with former Benfica player Victor Lindelof, Daley Blind, Juan Mata and Rashford returning to the side.

But it was Benfica who played the more enterprising football in the early stages as the visitors struggled to establish any rhythm and were frequently caught offside as they tried to make inroads.

United, unbeaten since they lost the European Super Cup to Real Madrid in early August, have made an impressive start to the season, scoring freely before the weekend's Anfield stalemate.

But defensively the three-time European champions have also been solid, conceding just six goals in 13 games in all competitions.

Svilar beat Iker Casillas's record -- the Real Madrid legend made his debut in the competition in 1999 at the age of 18 years and 118 days.

United, who did not qualify for the Champions League last season, now have nine points out of nine in Group A and look almost certain to qualify for the knockout stages but Benfica, without a single point, have a mountain to climb.