Gareth Southgate has admitted after seeing video replays of Manchester United's vital penalty that he is still unsure of whether it should have been awarded.
Referee Mike Dean pointed to the spot after Jonathan Woodgate appeared to catch Cristiano Ronaldo when attempting to make a saving tackle in the area.
Sections of Boro's back-room staff felt the spot-kick should not have been awarded and Southgate claims he is still not sure whether it merited a penalty.
"I am still not sure and I have seen it three times," Southgate told Sky Sports. "Sir Alex will say it is, but I don't know.
"The ref said it was and that's it, end of story."
Southgate felt his players could have done more to stop the move earlier, but was full of praise for their effort on the night.
"We possibly did not defend it so well up to him getting in that position, but there have been some fantastic performances from my players tonight and I am not going to knock them," he added.
"They have come to the best team in the country and run them all the way."
James Morrison saw red for a wild lunge at Ronaldo in injury-time and Southgate feels the midfielder will learn from his mistake.
Southgate added: "He is a young kid and he will learn a lesson from that.
"We would all in that situation love to do what he did but you have got to be mature enough and hold your ground and make the right tackle."