The Red Devils have conceded 21 goals in 15 Premier League matches so far this season and have shown the propensity to concede first in matches.
United will head into the derby against Manchester City at the weekend on the back of a 4-3 away win against Reading on Saturday, and Evans wants them to start improving defensively.
"We have to eradicate the mistakes," he is quoted as saying in The Mirror.
"We don't want to concede goals and give teams a chance to beat us or even take points off us.
"But whenever we go a goal or two behind we never feel like we are out of the game."