Oxford United manager Michael Appleton has claimed that Middlesbrough's winning goal in their 3-2 victory over his side this afternoon should not have been allowed to stand.

The U's looked to be on course for a fifth-round exit from the competition when they fell 2-0 down to their Premier League hosts at the Riverside, with Grant Leadbitter opening the scoring from the penalty spot before Rudy Gestede doubled the lead.

Two goals in as many minutes saw the League One side level things up, though, only for Cristhian Stuani to seal a dramatic win for Boro in the 86th minute, firing them into the quarter-finals.

However, Appleton felt that Alvaro Negredo was fouling Curtis Nelson in the build-up to the goal and was also unhappy at the referee's decision to wave away a penalty claim for his side.

"There were no issues with the penalty, it was a definite penalty. I thought Stewart Downing was excellent in terms of he was very clever where he took his first touch and he used the pace of Mags trying to get back in, so I have got no issue with that at all," he told reporters.

"But I have a lot of issues with the one we didn't get and then the one they won with, but I'll leave the officials to describe why that was given and wasn't given. Negredo was just pinning Curtis Nelson, he was just grabbing his shirt so he couldn't attack the ball and obviously that affected the first contact.

"They got a little bit of luck - Negredo just got a bit of a nick on it when he tried to do the overhead kick - and to be fair, it was a good finish at the far post."

Oxford are next in action on Tuesday when they face Charlton Athletic in League One.