The Spaniard has been impressed with 20-year-old Gibson's development this season, which has seen him thrown in at the deep end at times with injuries and suspensions taking their toll on his squad.
However, the head coach insists Gibson still has much to learn and wants to keep his feet firmly on the ground.
Karanka told the Northern Echo: "Ben Gibson has impressed me a lot so far since I have been with the club.
"He has shown he is a good defender and that he can grow as a player, but he needs to improve a lot too.
"His character is good. His ability is good too which has impressed me. But he has made mistakes as well, so he will get better with more games and experience."