There have been reports that the likes of Patrick Bamford, who is on loan from Chelsea, has been given assurances over how often he will play, but the Spaniard has dismissed those claims.
"The only pressure I have is to win the games," Karanka told GazzetteLive. "Because of this pressure I have to choose the best players.
"I will never have pressure from this club or from the clubs whose players are with us on loan.
"I don't want to have conditions on the player that I have to play them. For example, Bamford is here and I never promised him that he is going to play."
Middlesbrough are currently ninth in the Championship.