Karanka and co have earned plenty of plaudits for their performances during a recent tough run of fixtures, taking six points from the last five games, a sequence that has included facing Arsenal, Manchester City, Chelsea and champions Leicester.
While the Teessiders feel they could have taken more points from the games with the Gunners and Foxes, Karanka believes the team have made great strides following a worrying start to the season.
The Spaniard feels the turnaround began with the 1-1 draw at West Ham at the start of October, which ended a run of three straight defeats, claiming performances have steadily improved since that result.
"I am optimistic after the game against Leicester but for me it was the same after the game at West Ham," he told the Gazette.
"That was a key moment for us. We lost against Tottenham and we were really, really poor, especially in the first half, but West Ham was an improvement and it was important.
"Against Watford, even though we lost, we were a little bit better. And after that we have played very well against Arsenal, Manchester City, Bournemouth, Chelsea and Leicester.
"We have grown a lot. The best way to add experience is by adding points and we have shown how good we can be."