The Red Devils, who earned their place by winning last season’s Europa League, have claimed four victories from their four Group A games and need just a point from their remaining two games to progress.
“We have not qualified yet? Four victories and it is still not enough? We must get that point from the two remaining matches,” said manager Jose Mourinho.
“I am more than happy. We changed a lot of players, we broke the natural dynamic and routines of the team and we played a kid (Scott McTominay) from the academy.
“We scored two goals, did not concede, gained three more points, more money for the club because every victory means money and did not have any significant injuries.”
Anthony Martial, who provided a threat from the left with his trickery and pace, earned a penalty when he was tripped by Douglas, but the Frenchman had his spot-kick kept out by Mile Svilar.
Belgian goalkeeper Svilar also twice saved well from fellow countryman Romelu Lukaku, but a mistake on his debut in the competition in the previous game contributed to United’s narrow victory and he gave the hosts a helping hand again.
Ex-Benfica midfielder Nemanja Matic’s powerful shot struck the foot of the post, but ricocheted off the unfortunate Svilar – who had dived to save the shot – and into the net. Full-back Daley Blind added a second from the penalty spot.
The Portuguese champions were much improved from the reverse game and offered more of an attacking threat, forcing David de Gea into two excellent saves in each half.
The home goalkeeper denied forward Diogo Goncalves’ curling effort towards the top corner and low shot across goal, while he also gathered Raul Jimenez’s long-range drive.
Mexican Jimenez intercepted Eric Bailly’s lazy cross-field pass deep inside his own half, but his shot cannoned off the post.
In the group’s other game, CSKA Moscow came from behind to beat Basel, leaving United six points clear but waiting to go through.
The Premier League side face a trip to Basel next month, followed by their final group game at home against CSKA in December as they look to go through to the round of 16 where they last played in under David Moyes in 2014 .-BBC