Aitor Karanka has expressed relief over Middlesbrough's 3-2 win over Oxford United in the FA Cup, but warned his players not to lose their concentration in future.

The League One visitors were on the cusp of claiming a draw after scoring two goals in quick succession to nullify Boro's initial two-goal lead, only for Cristhian Stuani to strike late on and see his side through to the quarter-finals.

Karanka told BBC Sport after the game: "It was a typical FA Cup game, so when you think everything is under control you concede two goals in one minute. Now it is nice because we won the game, but at the time the other manager would have been really pleased.

"If you lose your attention, even against a League One team, it is the biggest mistake. To compete in this country you always have to play 150 percent, even teams two divisions lower can create you problems.

"Three years ago I don't think anyone would believe we would be in the Premier League and quarter-finals of the FA Cup."

Boro will find out their quarter-final opponents in Sunday's draw, which takes place at 6.30pm.