The Argentina international has already delivered decisive contributions against Pep Guardiola's side, including a last-gasp equaliser at the Etihad Stadium earlier in the campaign and a bundled finish from close range in another meeting.
He also arrives at Wembley fresh from scoring in the draw against Liverpool, continuing his habit of producing in key matches.
Interim boss Calum McFarlane has been clear about Fernandez's influence on the squad. "When it gets tough, you see the fight in him," he said. "You see him driving the group on, making tackles, fighting for every loose ball."
Fernandez, who will reach 150 starts for Chelsea in the final, has operated mainly as a No 10 behind Joao Pedro, using his energy and movement to press high and arrive late into the box. Eight of his nine league goals this season have come from inside the area.
McFarlane also highlighted his timing. "His runs into the box, his ability to get height and distance on his jump, his heading technique is really good," he said after the win over Leeds United.
His season has not been without controversy, including an internal ban following comments linked to Real Madrid, and a two-match exclusion earlier in the campaign under former coach Liam Rosenior.
But McFarlane insists the mentality is clear. "He's a winner," he said. With Manchester City defenders Abdukodir Khusanov and Marc Guehi expected to track his movement closely, Fernandez now has another chance to define a season at Wembley Stadium.