Boro have been overtaken by both Hull City and Burnley in recent weeks, and they have slipped down to third place in the second tier standings.
And Karanka admits that his side will now face a tough test if they are to move back up the table.
“It is a big challenge,” Karanka said. “I like this challenge especially with these players. The last two games we have not won. But we have had chances to win, against Leeds and MK Dons.
“We will start winning again. We have good players and we are playing better than we did against Forest, Bristol City and Blackburn.”
Boro’s performance levels have dipped in recent weeks, and their results have reflected their drop in standards.
The Teessiders have stumbled since losing to Bristol City in the middle of January.
Middlesbrough have failed to win any of their last five matches, despite investing heavily in January.
Karanka brought in the likes of Gaston Ramirez and Jordan Rhodes last month, but the new recruits have not sparked Middlesbrough into life just yet.
Despite their poor form, Boro are still within touching distance of the top two - and they could move back to the top of the pile, if they are able to beat Cardiff City at the Riverside Stadium later this evening.