Boro have failed to win any of their last three Championship matches, meaning they have slipped behind Hull City at the top of the table.
And after watching his side draw 1-1 with Blackburn Rovers at the weekend, Karanka is now set to make a number of alterations to his starting line-up.
“I prefer to think about the last 20 minutes and to think about the game on Tuesday,” he said.
“With the players today thinking the reaction was going to be better. I had to be fair with them because we’re in the position we are because they have been playing well until two weeks ago.
“Now I’ve seen that reaction and I have to think about changing something.”
Karanka only started two of his five January signings in Middlesbrough’s match against Blackburn, but it seems likely that some more of the new recruits could get a chance against MK Dons.
That looks set to be good news for Jordan Rhodes, who only had a brief amount of time to impress for his new club on Saturday.
Rhodes entered the field with 20 minutes to go, but it was Dave Nugent who grabbed the equaliser against Blackburn.
Boro are currently in second place in the Championship standings and, despite their poor run of recent results, a win on Tuesday would send Karanka’s men back to the top of the table.