AITOR KARANKA believes Middlesbrough will not be an unknown quantity to Arsene Wenger when the Teessiders attempt to shock one of the Premier League’s best teams for the third time this season.

Boro’s hopes of leaving Arsenal this weekend with a place in the FA Cup quarter-finals have also not been helped by the news that Spanish defender Daniel Ayala has been ruled out for up to four weeks with a thigh problem.

While Karanka, who is unable to call on Tomas Kalas because of the terms of his loan from Chelsea, is confident in the men he does have available for the trip to the capital, he knows the task has been made harder by Middlesbrough’s success so far this season.

As well as leading the Championship after an unbeaten run dating back to before Christmas, Karanka has also led his team to memorable performances in both the Capital One Cup and the FA Cup.

Before the 2-0 victory at Premier League champions Manchester City last month, Middlesbrough took Liverpool to penalties in the Capital One Cup in September when it took a mammoth shoot-out to knock them out.

Karanka said: “It is going to be difficult, very difficult. Arsenal are another Champions League team with an amazing squad, you can say that they have some players injured but they still have a very strong squad. It’s a good challenge for us, and for everybody to watch Middlesbrough again.

“I think Liverpool could have been a surprise, Man City was a surprise, but now everybody knows Middlesbrough, we played very well against City – very defensive, but very good – and we are top of the table now so for Arsenal it is not going to be a surprise.”

It will be a case of going from one extreme to the other for Middlesbrough. Just days after having to overcome the worst pitch in the Football League to claim three points at Blackpool, Karanka must take his team to a surface which is made for Arsenal’s free-flowing style.

“We are going to play on one of the best pitches in the world, so it’s not an excuse if we don’t cope with it,” said the Spaniard. “It wasn’t an excuse at Blackpool. It was impossible to play, but there’s going to be a difference at Arsenal.

“It’s easy for me because I have been working since the beginning of the season to have a better squad. I made changes on Tuesday, despite the players being perfect on the Saturday, and now I can play with these players or change them around, because all of my players are ready.

“For me, the main thing is that my players are ready to play. Whether it is to be Blackpool, Man City, Arsenal, whoever, I have 22 players always ready to play.”

Even if Middlesbrough can knock Arsenal out of the FA Cup, he does not think making further progress in that competition will distract his team from the main goal: Promotion to the Premier League.

He will be doing everything he can to try to defeat the Gunners, even if he is wary of the threat posed by one man he worked with during his time as Jose Mourinho’s assistant at Real Madrid.

“Mesut Ozil’s a very good lad. I spent three seasons with him and he’s an amazing player,” said Karanka. “I hope on Sunday he doesn’t have his best day. I hope he can rest for the league because they have some important games coming up. It’s not just Ozil, it’s Santi Cazorla too; they have a lot of players though.

“But in the same way that Liverpool and Manchester City are very dangerous when they have the ball, they can have problems when they don’t have the ball.

“The trick is to keep the ball against them. Again, we’re going there to play, in the way we know we can, and we’re going to try to win, while always knowing that it’s going to be difficult.”

Ayala, meanwhile, has received the bad news after being assessed following his withdrawal at Blackpool on Tuesday. Jonathan Woodgate is pressing Kenneth Omeruo and Ben Gibson to start.

Left-back George Friend has returned to training after illness, while midfielder Adam Forshaw is cup-tied having played for Wigan in the FA Cup already this season.