United fought back from 4-2 down in extra-time to win 5-4, reaching the Europa League semifinals 7-6 on aggregate.
It was Maguire who headed home the final and fifth goal and he said afterwards: "Obviously it's an incredible game, we made really hard work of it. We had full control in the second half, had chances to score a third, then they scored out of no where. It put us on the back foot.
"To go down 4-2 in extra-time to 10 men is not good enough, we opened ourselves too much. But we dug in and showed great spirit, that's what this stadium does."
On his goal, Maguire also said: "I felt like the fourth goal for them was a sucker punch but that we'd get chances to get back into it. It fell to myself and thankfully I scored, it was an amazing feeling."
On if he fouled his marker to score, the defender insisted: "He was back-pedalling but I just held him there, with my hand, there was no where near enough for a foul."