The Spanish giants are widely expected to bring a new midfielder to Camp Nou ahead of the 2017-18 campaign, with Paris Saint-Germain's Marco Verratti strongly linked with a move to Spain.
Fernandez has said that Barcelona are looking for "a big player" that has the capabilities to "play in all three positions" when it comes to midfield.
"It's difficult because we have an amazing team. Whoever comes here has to be a big player," Fernandez told reporters.
"A player who can play in all three positions would be amazing, because playing in that position means you're always fighting for game time so the more positions you can play in, the more opportunities you'll have."
Barcelona relinquished La Liga to Real Madrid last season, although they did land the Copa del Rey crown.