Fernandez struggled with knee problems a couple of months back and had was sidelined for a few games for the Blues. He even pulled out of back-to-back Argentina squads during the October and November international break as he did not want to aggravate his injury further ahead of his nation's title defence campaign in North America next summer.
Before pulling out of the national team squad in November, the midfielder had said: "I will not be available with Argentina. I was just talking to the medical team because I had a problem with my knee in the last four months. I came with a bone edema that got worse in the last weeks and months because we played a lot of games. I think the most important thing is coming to the end of the season and I think it's good to make this decision together. Always respecting the doctors and everything."
Fernandez will be back in action for Enzo Maresca's side on Saturday as they host Everton in a difficult Premier League fixture at Stamford Bridge.