United only managed a 2-2 draw at Old Trafford in the first leg.
“When you are the European champions it gives you the confidence to believe that you are never out of it,” he explained to the Sunday Mirror.
“We still think we can go to Porto and win. Now it’s up to us to go over there and prove it.”
“Drawing the first leg at Old Trafford 2-2 wasn’t ideal, but it’s not the end of the world either because if we go there next week and win, we are in the semi-finals,” he continued.
“It’s going to be a lot tougher than we would have liked in the second leg, but we aren’t getting down about things.
“It’s now just a case of getting the balance right again. We haven’t been defending well as a team in the last few weeks and it isn’t ideal having to score two or three goals to win.
“We all stick together at Manchester United and we still believe that if we get back to doing the right things we can bounce right back.”
“We are well aware that Porto have a great record at home and I’m told that no British club has ever won over there,” he added.
“The only thing I can say to that is that Manchester United are all about making history and breaking records.”
