Erik ten Hag slams Forest for 'targeting' Bruno Fernandes in Man Utd win
Fernandes featured in United's 1-0 victory at the City Ground despite a "serious injury" suffered in last weekend's loss against Fulham.
The Portugal star delivered the free-kick that Casemiro converted in the 89th minute to seal a quarter-final clash with bitter rivals Liverpool.
Fernandes was on the receiving end of robust challenges from Forest throughout the 90 minutes, just days after United's captain was the butt of social media jokes following his injury against Fulham.
Fulham's official TikTok account poked fun at him for appearing to feign the problem on Saturday.
But Ten Hag said Fernandes has often played through the pain barrier after the kind of rough tackling he was subjected to by Forest, which left him limping at full-time.
"I don't want to go into that because you saw that Forest was targeting him, so I don't tell what he has but it was a serious injury," Ten Hag said.
"There were many fouls on him. Maybe I am a little bit too tough but when he has the ball they were really tight on him.
"Then I see that serious media criticise him and social media is pathetic and it can't be.
"He has a serious injury but he continued to play on Saturday and today he also fought to be part of the game and he has a very high pain threshold.
"Last year he did also something similar against Spurs and it shows his leadership because that expresses his character and that is very good when you are a leader."
United, who face Manchester City in the Premier League on Sunday, kept alive their last chance of winning silverware this season despite a scrappy display.
But Ten Hag knows facing quadruple chasing Liverpool in the last eight means United are far from certain to land the second trophy of his troubled two-year reign.
"There are many good teams in the Premier League, Liverpool at this moment is top but it is a great challenge and we are really looking forward to it," he said.
"We like the challenges. It's a great game for us. But first of all we are now looking forward to Sunday."