Nancy boss believes that the central defensive pairing have got all the attributes required to act as a strong foundation for les Bleus' defence
The two defenders helped France to keep a clean sheet, which continued the side's run of good performances, following the goalless friendly draw with Uruguay in August.
"They were strong against Uruguay and they performed [again] in Finland, which was another challenge with pressure," explained Fernandez, speaking to FranceFootball.fr.
"They emit a strength, power and speed that makes a modern defence. These are two players with personality in a position which requires it."
The Nancy boss also gave his thoughts on France's future, something which he believes the defensive duo will be heavily involved in.
"This is very encouraging for the future. They open other perspectives for Didier [Deschamps] in this key sector."
France face Belarus in their next group match, with Yanga-Mbiwa and Sakho highly likely to be involved.