The Portugal international played the full 120 minutes of the enthralling last-eight fixture at Old Trafford, which was decided by a last-gasp goal from Red Devils attacker Amad Diallo.
Liverpool led 3-2 in extra time but ultimately lost 4-3 in Manchester, with Erik ten Hag's side advancing to the semi-finals, where they will take on Coventry City for a spot in the final.
Fernandes was seen hobbling towards the end of the match and even dropped back into central defence during extra-time, and there had been fears that he had suffered an injury in the FA Cup contest.
However, the 29-year-old has said that «tiredness» was his main issue against Jurgen Klopp's side, with the midfielder calming suggestions that he picked up a fitness issue.
«I was shouting and I couldn't hear my voice. So you have an idea of what the noise was like for us on the pitch, with the tiredness, with everything,» Fernandes told TNT Sports Brazil.
«My lungs were on their last legs too… but it was impressive. I think they were excellent with us from start to finish, even when we conceded a goal, because the next moment we'd create something and the stadium would rise up again and create the momentum we needed.
»And at one point I had to jump into the middle, at others I had to drop a little deeper, because my legs were getting tired, I was cramping up everywhere, and I even took a knock to help out.
«But it's whatever it takes to help the team. Because Antony ended up at left-back, [Christian] Eriksen was also at six, [Scott] McTominay further forward. We were all giving everything we
Read on sportsmole.co.uk