The Belgium international looks set to leave Stamford Bridge in the summer with Real Madrid the widely touted destination.
Hazard, who has won the club’s player of the year title in four of the last six years, has refused to comment on his future at the Blues all season.
Reports in France suggest an agreement had been reached and the deal would be announced following the Europa League final on May 29.
Derby County manager Lampard, who played with the 28-year-old for two seasons at the end of his Chelsea career, said it would be a big loss if Hazard were to leave.
“He’s in the top few players in the world. I think we all know that,” He told talkSPORT.
“We’ve seen him in the Premier League and he has been a joy to have. He was a joy to play with.
“I knew his potential from day one when he trained at Chelsea a few years ago now.
“Of course it will be disappointing to lose him for the Premier League but particularly Chelsea.
“You don’t replace Eden Hazard, you have to find ways around it whether it be some of the younger players or the team.
“That’s if you are going to lose him, we don’t know that for sure yet but it seems it might happen.”
Lampard believes his former club need to just focus on the Europa League final in Baku rather than who may or may not be leaving in the summer.
He added: “The Europa League final will be a huge game for them. To win a competition like that is always big.
“It’s going to be a tough game against Arsenal and then we will see with the transfer ban etc.
“It’s always news at Chelsea. It’s always happening that way when you are a big club it tends to be that way. We will see.