Boro led 1-0 in the Championship clash at the Riverside Stadium on Tuesday evening before Darius Henderson's controversial late equaliser snatched a point for the visitors.
It was the first goal the Teessiders had conceded on their own pitch in almost 12 hours of football, but Karanka was not too downhearted.
He told the club's official website: "We had a lot of chances in the second half and we deserved to win the game.
"I'm happy because we have a lot of injuries to defenders and keepers and we are fighting with teams in the play-off positions.
"I'm happy because I have a team who when we work, we can win every game - and I repeat, we deserved to win."