Reina was at fault for the opener as he allowed Sergio Aguero's speculative shot from distance to go under his body after misjudging the flight of the ball.
However, the Reds boss refused to single out the goalkeeper for criticism.
"We are not going to sit and isolate individuals because you don't win a thing with individuals," he said.
"Every single one who played made a mistake in some form. It is how we react to them that is going to be important."