The result lifted Reading back into the playoff spots and Karanka has admitted that Boro, who saw their own hopes of a top-six finish ended with defeat to Millwall last weekend, did not match the desire shown by their opponents, and criticised them for being passive.
"One team was playing for the points, the other team was playing for nothing," he told reporters. "If Reading had needed more goals they could have scored them.
"It was my fault. It's difficult when you don't play for points but I didn't choose the right players and I couldn't motivate them. As a player I was competitive and I want competitive players."
Boro are now an unassailable nine points adrift of the playoffs, with two games of the season remaining.