The Serbia Under-19 international has joined on loan from Tottenham Hotspur until January following on from Ryan Fredericks’s recent arrival from White Hart Lane.
Veljkovic can operate as a defensive midfielder and also at centre-back, where Boro head coach Karanka feels he is best suited.
He said: “For me, he is more of a central defender. In the last two games (for Serbia Under-19s) against Spain, he played as a central defender.
“But I will use him in the position where we need him most.
“He is here to challenge for a place in the team. If he gets his chance and takes it, he will keep on playing as I always say that the age of a player is not important to me.”
Boro duo Ben Gibson and Patrick Bamford are hoping to round off a fine week today, having helped England Under-21s to play-off glory against Croatia to qualify for next summer’s European Championships.
Karanka says he has received positive feedback from Under-21 head coach and former Boro manager Gareth Southgate with the Basque particularly pleased for Gibson, pitted in an ongoing battle for his first-team place at Boro.
He said: “I had some very good feedback from Gareth about Ben and Patrick, but especially about Gibbo because he was the player who played (against Croatia).
“It is important for him. He lost his position in the team for the last couple of matches, but he has recovered his confidence and that is good.”
Boro have sold out their 2,600 allocation for the trip to Rotherham on November 1.