Messi's current contract runs out in 2018, having last signed an extension in the summer of 2014.
"Leo's renovation is going very well, very well," Fernandez told RAC1. "I'm very relaxed, as I was before with [Javier] Mascherano, [Sergio] Busquets, [Luis] Suarez or Neymar.
"And I am now with Messi, as I am with Andres Iniesta or [Marc-Andre] Ter Stegen. We're working and I'm convinced that they'll continue with Barca.
"It doesn't matter much who will be the first to renew. There will be people who want to poison the situation, but we've been working on this issue for a long time."