AITOR Karanka was relieved to edge through in the Emirates FA Cup after Oxford United punished his Middlesbrough side’s lapse in concentration.

The Premier League side looked to be cruising into the quarter-finals when they reached half-time 2-0 ahead.

But the second half was a different story, as United hit back to draw level and had chances to win the game before Cristhian Stuani’s 86th-minute winner to send them through 3-2.

Boro boss Karanka said: “I had said before the game Oxford were a really good team, they beat Newcastle in the last round and I said we had to be really careful.

“We had the game completely under control because our approach to the game was completely different to the last round when we played Accrington.

“But, once again, when you think everything is done, you are making a big mistake.

“Even playing against a really good League One team you always have to concentrate 150 per cent, especially in this country.

“When you lose your concentration and think everything is done, it’s a big mistake.”

He added: “We conceded two goals and we are in the next round, but it is a good lesson for us for the future.”