Fernandez, who joined Chelsea for a British record fee of more than £120million, has struggled at times since his move - most notably when he was left in the dust by goalscorer Karim Adeyemi in Borussia Dortmund's 1-0 Champions League win over Chelsea last month.
In Chelsea's last three games, however, he has been a considerably more settled presence in midfield alongside Mateo Kovacic (28), and the Argentine provided a sublime assist for Kai Havertz (23) on Saturday.
"He's a fantastic player. He's a young player," Potter told reporters.
"He's going to get better and better as he's with us more, because he's just arrived from another country and another league. So you always have to adapt to that.
"But you can see his quality, he gets the ball, he can pass forward. He's progressive with his mentality, gets the team moving, and then he gives everything so it's a nice combination to have."
Potter also heaped praise on another January signing Mykhailo Mudryk (22), who looked lively in his first start since February 15 as he had a goal ruled out for offside and recorded an assist for Kovacic.
"He wants to help the team wants to work with the team," Potter said. "So delighted for him that he could assist and help us win."
The English manager added that he was pleased with the spirit and togetherness shown by his players, calling on them to enter the coming international break on a high with a home victory over Everton next week.
"Everyone's supporting each other, fighting to play. I'm delighted for the players, because it's been a tough period we've been through but this week has been a positive one," Potter said.
"Now we can look forward to the weekend against Everton and try to finish up before the international break with three points."
Check out the game summary from the Blues' win against Leicester with Flashscore.
