They are now through to the semi finals to play Coventry City, after beating Liverpool in the quarter finals on Sunday.
"It is a tough game," said Fernandes to club media.
"I see some some of their games because my chef at home is a Sunderland fan, so I get to see some Championship games sometimes with him at home.
"So for some spells they have good players on the ball. They are really difficult to play against physically. We saw it against Wolves.
"They won the game in three minutes I think, 97 and 90 plus 10, something like that. So we know what to expect and we can't be getting there and be surprised for what they're going to bring to us.
"We have to do the same as we did today on running, on tracking back or fighting spirit and everything, and then put the quality we have put on in the 30 minutes today for longer spells in the game."