Clement brought the Portugal star to south Wales on loan by using his contacts at old club Bayern Munich.
He told The Times: "He wasn't so keen [on coming to Swansea] initially.
"He thought he was going to go to Man United, Chelsea or Paris Saint-Germain.
"Bayern were saying, 'You're not going there, it would be the same situation, you're not going to play'.
"When he came, he was far more damaged than I thought. It was really sad.
"He was a boy who had almost got the weight of the world on his shoulders.
"In training, when that pressure is not there, he was the best player.
"He could do things no one else could do. He's got power, can go past people, got a shot on him.
"But then in games, I looked at the choices he was making, shooting from 45 yards on the angle, and he kept making those mistakes.
"He had a desire to please and a desire to prove everybody wrong. He got in a vicious cycle of poor choices.
"The other players were saying, 'He's playing like that and you're not picking me,' so it became difficult to pick him."