Yet each time, the Macau international, 18, ignored the doctor's advice - and refused to quit the game he loves. And last month Leong's determination was rewarded when he was named Macau's Footballer of the Year.
Yet the coveted award - voted for by his peers, Macau's football journalists and the board of directors of the Macau Football Association - was not the attacker's only success. He was also named Best Local Player of the Year, Best Under-23 Youth Player and selected among the Best 11 Macau Football Stars.
"I knew I was in the running for Footballer of the Year, but I didn't feel stressed," says Leong, who has just started studying for a degree in communications at the University of Macau.
"I was competing at the All China Secondary Schools Students' Games, in Baotou, Inner Mongolia, in July when the voting for the award took place. I'd actually almost forgotten about it until a friend told me on the phone that I had won it."
Leong, a key player for Macau's national team, helped them finish fifth out of the 12 football teams at the Games - their best position ever.
"Compared to Hong Kong, we face big challenges," he says.
"The biggest obstacle to progressing as a team is that we have few full-time players in the team. Many Macau players have a day job so they may not be able to take time off from work to play in overseas tournaments."
His individual awards were particularly sweet because of the uncertainty he faced after breaking his arm three times and being advised to quit the game he loves.
"I broke it when I was 15, then again when I was 16. Both times the doctor told me I should stop playing, but I didn't listen to him," Leong says.
"Then I broke my arm again soon after that. But I still wanted to play. So now whenever I play, I wear a plastic protective guard on my left arm. And I have no problems."
His awards came after a fine season with MFA Development, an under-21 team playing in Macau's First Division.
"Our league team was formed by the Macau Football Association to offer young players more chances to compete and train together," he says. "In past seasons, the team have come close to being relegated a few times, but last season we finished fourth out of the 10 sides in the league. We are getting better and better; this season our goal is to finish in the top three."
Leong has enjoyed being the focus of local media attention in Macau because of his success. "I am very happy to have won the awards, but I am keeping things in perspective," he says. "I know I must keep up my standards, or people may forget about me very soon."
Before the new season started, Leong had an offer to play for a Hong Kong team. He considered following in the footsteps of Sunhei goalkeeper Domingos Chan, 41, the first Macau footballer to play in Hong Kong, but in the end refused.
"I was at a crossroads in my life this year," he says. "I had a chance to study and play football in Japan - and I also had a place to study at the University of Macau. I decided to stay put for now.
"If I want to become a professional player, Hong Kong will be a very good option for me. But it is not practical to travel between Macau and Hong Kong every week; it would mean I could not study and play football at the same time.
"I needed some time to think about my future career path and I decided it is possible that I might come to play in Hong Kong next season if there is another offer."
The interest in him from journalists after winning so many individual awards has also reinforced his desire to work as a sports journalist one day. "I always read Young Post," he says. "It is delivered to my school every week and I always read it for assignments. But my English isn't good enough yet for me to become a journalist for an English-language paper, but I am interested in sports reporting for Chinese media in Macau."
His experience as a footballer will certainly give him an advantage over other candidates. "I want to write exciting reports, rather than just report the scores," Leong says. "As I am an athlete, I know what other athletes and sports fans want to read."
However, Hong Kong fans may not want to read about further success for Leong - for a while, at least. Earlier this year, he helped Macau to beat Hong Kong for the first time in more than a decade at the Interport Football Championships.
And next week he will be hoping to win again when he leads Macau against Hong Kong, Chinese Taipei and the Philippines in next week's Long Teng Cup in Taipei.