The capital club regained top spot in Ligue 1 by beating Troyes 4-0 at the Parc des Princes, helped by two goals from their Swedish striker, but Fernandez remains unimpressed by their current boss.
"When the PSG sought Ancelotti, they knew what they were getting," he explained on his RMC show Luis Attaque.
"Leonardo knows him well because they worked together at AC Milan. So when they recruited him they knew he came with a real resume.
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"We judge the coach on performances and results. And so far, we cannot always say that he has been good, very good, excellent or outstanding. The one saving Ancelotti's neck is Zlatan.
"You cannot say that the team are playing well or are making short work of things. That is not the case."
Fernandez went on to criticise Ancelotti for failing to find the best system in which to field his players, despite having time to settle into life in Ligue 1.
"He knows the league now. He has an impressive staff behind him. So for now, we're a little disappointed because he cannot find the right system.
"He only change players that are either out of shape or injured."