Fernandes had a penalty saved before scoring late on.
"We knew it would be a difficult game against Newcastle in their home," Fernandes told MUTV afterwards.
“After the goal we conceded, we played better but we need to improve. We can't concede as many goals as we have at the start of the season, and I think everyone agrees. The most important thing is that we win. We are happy for the game today."
Fernandes also saluted the mentality of Ole Gunnar Solskjaer's squad, coming back from an early Newcastle goal and the defeat to Tottenham last time out.
“I think the team has big characters and big players," he declared.
“What happened against Tottenham can't happen again. We play for such a big club and such a big team. This club deserves better than that. Everyone needs to be better, starting with me, I need to look at myself first and then at what the group needs to do better."