Callum Hudson-Odoi has admitted he was worried he would never play again after rupturing his Achilles last season.
The 18-year-old missed Chelsea's Premier League run-in, the victorious Europa League final and the Nations League with England as a result of his injury.
He has made an impressive return, registering three assists and a goal in four games, but told Sky Sports News about the doubts he encountered after sustaining the injury.
He said: "I wondered if I would be able to play again; that was my first thought. I knew I'd done something really serious so I was really concerned.
"But my family kept me confident that I'd be back to how I was.
"There were days when I would go into training and I would be sad or disappointed because I could see the boys outside training and you just want to be out there with them.
"So I had the dark days but at the same time I had positive days as well."
Hudson-Odoi's injury came just as he was establishing himself in Maurizio Sarri's Chelsea side, as well as the England senior team.
"When it came, it was more anger for me because everything was going as I wanted it to go," he said. "I was playing games, I'd got called to the national team - everything was going perfectly.
"There were big games coming up. But I knew when I came back I'd be stronger than I was before.
New Chelsea head coach Frank Lampard has praised Hudson-Odoi's impact since his return last month, and the winger said: "It's an amazing feeling.
"I was out for three to four months and it was crazy to even get the injury in the first place. It's something I had to deal with mentally because I'd never experienced an injury like that before.
"I'm really delighted with the way I've come back. I didn't expect to get this many assists and to contribute with a goal as well. Hopefully I'll keep improving and adding goals to my game."