Salah, who arrived at Liverpool from Roma in the off-season, has nine goals and two assists in 12 Premier League games this campaign.
Ahead of Saturday's meeting between Chelsea and Liverpool, Hazard was full of praise for Salah.
"He is still my friend. We are still in contact together. He's a top, top, top player," the Belgium international told reporters.
"He did not get his chance at Chelsea but we know, in the team, the quality he has. He is a fantastic striker and this season he has scored a lot of goals.
"He did not get the chance [at Chelsea]. Maybe because of the manager, because of the players, I don't know. But he is a top player for sure.
"In training he did everything. Even in the games when he was playing, sometimes he scored goals, so we know the quality he has."
Salah had loan spells at Fiorentina and Roma before joining the latter on a permanent basis, scoring 29 goals in his two full Serie A seasons.
Hazard said he too would have made a move if in Salah's position at Chelsea and he is happy to see the forward performing well.
"His feeling was good. When you are not playing at a club you need to go," he said.
"You need a chance and he took his chance at Fiorentina, so he did everything that you have to do when you are not playing.
"If I was not playing, I'd want to go. That's normal because all the players want to play. With him he did well and I am just happy for him."