The 2-2 draw ended a three-game winning streak for Boro and Karanka was not happy with his team.
Substitute David Ngog scored a last-gasp equaliser for Wanderers after Alex Baptiste cut the deficit to one in the first half.
"I think that this is the worst we have played since I came to the club," said Karanka
"I was disappointed that we could not hold on for the win, but I think that we didn't deserve to go 2-0 up and I'm sure that we can play much better than we did do here.
"We had five or six players who didn't play the last game, so I thought because of this my team could be a lot better than we were. I made the changes because I believe that they are the best 11 that I have at the club.
"But here we had no possession of the ball and we weren't comfortable on the pitch. We need to have the possession of the ball to keep them away from the counter-attacks.
"We played thinking that we were better than we are and we needed to play like we did in the previous three games."