The Foxes will never forget their incredible triumph in 2016, but begin the new year just six points above the drop zone and two in front of a Boro side who were not even in the division during their 5000-1 success.
Karanka saw his side beaten late on at Manchester United on Saturday, but believes games against bottom-half rivals are key to the Teesside club’s prospects.
And while Leicester are reigning champions, they fit that profile on current form.
“Now is the most important game in the season because it is the next one and it is against a direct opponent,” said Karanka.
“All this season these are the kind of games we have to win. We are playing at home and always I say if we are playing this way we will win games against our opponents like we did against Swansea, against Hull, against Bournemouth.
“We won them and that is the way to keep going. We know if we play with less intensity than we did (against United) we have problems so we need to play with at least the same intensity.
“I’m pleased with the way we competed and we will win games against teams who are playing to stay in the Premier League.”
When the sides met in the reverse fixture on November 26, Alvaro Negredo’s double put Boro on course for victory until the Foxes grabbed a last-gasp equaliser from the penalty spot.
Reflecting on that point at the King Power Stadium, Karanka added: “We forgot they had won the league, we were much better than them in the game and we keep going and play in the same way.
“We need to analyse Leicester again and their players. They cannot play with Jamie Vardy (suspended) so they will be different to how they were in Leicester. I don’t have a lot of time but time enough to prepare.”
Leicester boss Claudio Ranieri, meanwhile, has thrown down the gauntlet to Islam Slimani after the striker’s latest winner.
The forward scored to beat West Ham 1-0 on Saturday and the Foxes go to Boro still searching for their first Premier League away win of the season. Slimani now has six goals for the champions following his record £30m move from Sporting Lisbon in the summer.
Ranieri said: “We have to find him much better because he has very good quality and also presses a lot and sometimes he can make mistakes because he is very tired, but it is okay.”