The Argentine completed a move to Elche from Newcastle less than five weeks ago, signing as a free agent.
"We were speaking about my time at Newcastle and the relationship that we had," Fernandez stated.
"He said thanks for how I had been even when I was not playing. From my side, it was the same. I thanked him for coming to the club and helping us make a real impact to start winning games.
"Eddie and his staff, from day one, came in with a really good spirit and organisation with everything. The training was a huge change for us from what we had come from in terms of intensity and the detail, and how competitive it was. He tried to keep everyone fit and competing for a place. That was really good.
"I said to him and the staff when I left that they are in a very good place to have a future in Newcastle. They are well prepared."
"I spoke with a few of the lads when I left," he added.
"Matt Ritchie mentioned that with Jamaal [Lascelles] and a few others that had stayed during my four years, we managed to keep Newcastle in the league.
"He said, 'We had really good moments so don't underestimate what we have done'. This is something nice as well.
"We supported each other to try and get Newcastle in the best place. Now the situation has changed for the good but years before, as players, we tried to manage the team to improve everyone at the club. We did it well.
"Things were very different. We needed to stick together with the group we had. If someone came in, they had to have the same spirit to fight for the club and the fans.
"No matter what situation you are in, the fans will always support you with a full house at home so make them proud. They ask for this. In the end, we managed it. Sometimes, day by day, you don't stop to think about it, but what Matty said was right."