Real Madrid fullback Dani Carvajal admits he feared for his career over his heart problem detected last month.
He was initially ruled out indefinitely with the heart problem that left him in a very difficult state.
"I was scared and I thought that, if it was serious, I would have to retire," he explained to Diario Madridista.
"The first three or four weeks were the worst because I practically couldn't do anything, I couldn't raise my heart rate in any way and it was very low.
"The body demands activity, especially those of us who are athletes."
It appears that the derby with Atletico Madrid will arrive too soon for Carvajal, who has discussed the lengths he's been going to ahead of his return to the Real Madrid team.
"I would have liked to return sooner, but in the end we reached an agreement to do so after this international break," the defender added.
"That would serve to bring me back into the rhythm of playing competitively so that I'm able to face the whole month-and-a-half before Christmas.
"In principle I already have my medical discharge to start playing again, without any kind of problem. I don't think that anything will happen to me.
"I have trained a lot, aside from with the ball, adding to the sessions I have done in the gym and with the rest of the team. It has practically been like a mini pre-season."