AITOR KARANKA admits he has a selection headache ahead of Sunday’s crunch Championship game with Leeds United after his much-changed Middlesbrough line-up cruised into the fourth round of the Capital One Cup.

Karanka made seven changes from the side that beat Nottingham Forest last weekend, but the alterations did nothing to halt Boro’s momentum as a convincing 3-0 win over Wolves made it six wins in a row in all competitions.

Two goals from Albert Adomah, and a further strike from Diego Fabbrini, ensured Boro will be involved in Wednesday evening’s fourth-round draw, but Karanka is already turning his attention towards Sunday’s game with a Leeds side that did the double over the Teessiders last season.

The likes of Tomas Kalas, Fernando Amorebieta, Adam Forshaw and Fabbrini all returned to the side to deliver impressive performances, and Karanka admits he will find it especially hard to settle on a starting XI for the weekend’s game as a consequence.

“We changed a lot of players from Saturday’s game and they wanted to impress,” said the Boro head coach. “I told the players at half-time that I wanted to have a headache ahead of Sunday picking the starting XI.

“They were making it easy for me in the first half, but the second half was different. We were much better in the second half, and now I have that headache in terms of picking the team to play Leeds.

“The main thing was to win the game and get into the next round, and I am really pleased, especially with the second half. The attitude was really good, and I think we played a very effective game because we had three chances and scored four goals.

“It was good because many players have not been playing, but their performance, especially in the second half, was very good. I am really pleased with all of them.”

Karanka reserved particular praise for Carlos de Pena, who had a hand in both of Boro’s opening two goals as he made his debut following a deadline-day move from Uruguayan side Nacional.

De Pena started slowly from his left-midfield berth, but became increasingly influential as the night wore on and Karanka is confident he will improve as he gains more experience of the English game.

“I told him after the game that he now knows why it is not easy,” said the Spaniard. “He showed his quality, but he needs time. Whether it is in the league or the cup, football in this country is always difficult.

“I trust him a lot, and his team-mates trust him, but we need to keep calm with him because he will be an important player. He is a very good kid and he wants to improve. He can do much better, but I am really pleased with him.”

Victory followed hot on the heels of Saturday’s 2-1 win at Nottingham Forest, and means Boro have not slipped up since suffering a surprise home defeat to Bristol City in the middle of last month.

Their form is as good as that of any side in the country, but Karanka is refusing to get too carried away as the matches continue to come thick and fast.

“We have to keep going because we have done nothing yet,” he said. “It’s true that we have won six games in a row, but the main game now is on Sunday against Leeds.

“That is in the league and we are in a good position, but in this league if you lose three points or even a point, you can have problems.

“We need to forget the past. We need to know how good we are when we are playing well, but we have to keep going because we are only in September and there is still a long way to go."