Robinson said: "I always feel we are always in games and nearly all our fans stayed right till the end – they had belief that we could do something, and so did I.

"After Ben Stokes' effort for England against Australia (in Sunday's Ashes Test), comebacks are a big word at the moment.

"In England our sportsman do have a lot of grit and fighting spirit, and we showed that tonight.

"I've seen so many comebacks over the years, and if you do keep believing, it can work for you.

"I always knew this team had it in them. We showed that, if we stay in the game, then nick one, it's amazing what can happen.

"We had a blatant penalty in the first half that was not given. I was so surprised when Woodburn got that penalty at the end."

In the shoot-out, U's goalkeeper Simon Eastwood pulled off one fine save, while Bodvarsson – the best player on the pitch – missed his, leaving Oxford's John Mousinho to convert to send United through to the third round.

Millwall boss Neil Harris said: "I'm gutted that we lost the game because our performance didn't deserve that.

"We scored two, and it could have been four or six. It was a real dominant display by us.

"A deflected goal and a soft penalty cost us.

"It was an outstanding performance, with some strong individual performances but there was not that winning mentality.

"I'm pleased for Jon Dadi Bodvarsson. He has come in behind everyone else and has had to play catch-up.

"He has looked sharp in training the last seven to 10 days and he showed that with his finishing tonight."