Arsenal forward Gabriel Martinelli has the hunger and talent to become a world-class player for many years, according to Kieran Tierney.
Former Celtic defender Tierney identified the 18-year-old when he was asked which of the club's youngsters could become a world-beater.
Martinelli has 10 goals in all competitions this season and Tierney has been stunned by the Brazilian's ability since joining him in London.
In response to a fan from Reddit asking which player he was "most blown away" by, Tierney said in a Q&A on Arsenal's website: "I would say Martinelli.
"I think his hunger and drive and his talent together as one is more than enough to be a world-class player for many years.
"When I first did a full training session with the team I was put up against Martinelli and the intensity of his play was honestly mind-blowing.
"I thought to myself: this is the standard I need to be at to play for Arsenal."
Tierney was brought in for around £25million in August and leaving boyhood club Celtic was a life-changing decision for him.
"I would say leaving Celtic was the hardest decision I'd ever had to make and I knew I would always miss Celtic no matter what happens in life," added the 22-year-old.
"But the chance to play for Arsenal was a challenge that when I heard of it, I was just looking forward to it. I didn't move to Arsenal to live in London. I came to London so I could play for Arsenal.
"I miss everything about Celtic. And I always will. I am very grateful for every second I spent playing for the club."
In response to another question, Tierney revealed Paris Saint-Germain star Kylian Mbappe was the toughest opponent he had ever faced.
"Mbappe was the quickest and sharpest that I've come up against," he said.