Casemiro was at the centre of two mistakes in United's loss to Liverpool and has come under a load of criticism as such. Fernandes has also defended the underfire Brazilian, who has struggled for form since the start of last season.
He said: "Casemiro is more experienced than me, he played for the two best clubs in the world in terms of media coverage. He has a lot of quality. And mistakes are going to happen to everyone. We just have to be more cautious when they are about to happen and compensate and correct them in time.
"We have to be more alert when we lose the ball, feel and smell the danger and be more objective. Whenever we have opportunities, we have to score more goals. We have attacking quality, but few goals."