The Portugal captain has come in for criticism in recent weeks - alongside head coach Michael Carrick - after managing just one Premier League win so far in 2026/27.
Fernandes set a Premier League record last season after 21 assists - but he's only managed one in 2026/27 - with three goals scored.
Speaking on Rio Ferdinand Presents, Herrera claimed those calling out Fernandes should keep in mind the weight of responsibility he's shouldered in recent years.
"For me, he’s a leader. He's had Man United on his back a lot of years, a lot of seasons.
"In difficult times he' there, always putting his face there, asking for the ball, scoring goals, assisting. After defeats, going to the media to talk. I have huge respect for him, for what he has done for the club.
"He could have left the club and he’s still there and he deserves credit. A lot of credit. How can Bruno be the problem? He's been a solution a lot of time."