Lucas fell out with Emery while they were together at PSG.
He said: "It was very hard, the worst seven months of my life. I came from a very good season, I was second top scorer of the team, only behind Cavani.
"The following season, I wasn't even called up.
"I used to go to practice, I wasn't even in the game. I used to go back home.
"Anyway, it was very difficult. But I kept working hard, strong. And God gave me the best gift of life, my son."