Aitor Karanka has told his Middlesbrough players that they must up their performance levels and remain switched on throughout if they are to have any chance of beating Everton this weekend.

The Toffees have looked impressive in the early stages of Ronald Koeman's tenure, remaining unbeaten in their opening four Premier League games and winning the last three on the bounce.

Everton really turned on the style in the second half of their last outing, a comfortable 3-0 win over Sunderland, with Romelu Lukaku scoring all three in a deadly 11-minute spell in front of goal.

Karanka, who saw his side punished by Crystal Palace's Christian Benteke last weekend in a 2-1 home defeat, believes that Everton pose Boro's toughest test yet on their return to the top flight.

"We had a good test last Saturday with Benteke and we suffered against [Lukaku] last season when we played them in the cup, so it's nothing new for us," he told reporters. "We all know what a good player Lukaku is and how important he is for them but we can't think that it's just Lukaku.

"They have really good players and a really good manager so it's going to be a really tough game but we've been working for two-and-a-half years to play in these kind of games. My main game is Everton and it's going to be really, really tough but we have to know how good we are paying in our intensity.

"They beat us in the cup last year but they had to play their best and even in moments in the game we were better than them. With teams like Everton we have to be even more concentrated than we usually are."

Everton won last season's League Cup quarter-final clash between the two sides 2-1 at the Riverside Stadium - goals from Gerard Deulofeu and Lukaku inside the opening half-hour earning the Toffees victory.