The Brewers, managed by ex-Boro favourite Jimmy Floyd-Hasselbaink, are eyeing another cup shock after beating Bolton Wanderers 1-0 in the first round.
Karanka, whose side are reeling after a surprise home loss to Bristol City at the weekend, says that the winning mentality fostered by promotion last term for Burton – who knocked Boro out of the FA Cup in 2011 – marks them out as a real threat.
Karanka said: “We couldn’t beat Preston or Bristol City, two teams who got promotion last season.
“Burton got promotion from League Two to League One, so they are in a good way and we have to work a lot if we want to win the game.
“When you play against a team which is in a division above you, it is another motivation.
“It will be a difficult and tough game. I think it will be (a tougher test than Oldham in round one).
“Especially after our defeat on Saturday (to Bristol City), they now think they can beat us.”
Tonight’s game is one that Hasselbaink, who spent a rewarding time at the Riverside Stadium under Steve McClaren from 2004 to 2006, is relishing.
He added: “Middlesbrough are a club I know very well.
“The team has totally changed since I was there, but Boro is a nice club that I had a really good time with.”
Last six: games Burton WWWLWW, Middlesbrough LDWWDL.
Referee: M Brown (East Yorkshire).
Last time: Burton 2 Middlesbrough 1; January 8, 2011; FA Cup.