BEIJING, Sept. 19 -- China's first and only Grand Slam winner Li Na formally announced her retirement on Friday, leaving the Chinese tennis yearning for the next superstar.

Following is her farewell and retirement letter:

For close to fifteen years, we've been a part of each other's lives. As a tennis player representing China on the global stage, I've trekked around the world playing hundreds of matches on the WTA tour, for China's Fed Cup team, at the National Games and at several Olympic Games. You've always been there for me, supporting me, cheering me on, and encouraging me to reach my potential.

Representing China on the tennis court was an extraordinary privilege and a true honour. Having the unique opportunity to effectively bring more attention to the sport of tennis in China and all over Asia is something I will cherish forever. But in sport, just like in life, all great things must come to an end.

2014 has become one of the most significant years in my career and my life. This year was full of amazing highlights, which included winning my second Grand Slam singles title at the Australian Open and sharing the extraordinary experience with my country, my team, my husband and my fans. It was also a year filled with difficult moments, such as having to deal with the inevitable - making the decision to end my professional tennis career.

The amazing moment in Australia was filled with joy, happiness and extraordinary sense of accomplishment. The task of finally making a decision to hang up my racquet felt a lot more difficult than winning seven matches in a row in the Australian heat. It took me several agonizing months to finally come to the decision that my chronic injuries will never again let me be the tennis player that I can be. Walking away from the sport, effective immediately, is the right decision for me and my family.

Most people in the tennis world know that my career has been marked by my troubled right knee. The black brace I wear over it when I step on the court has become my tennis birth mark. And while the brace completes my tennis look, the knee problems have at times overtaken my life.

After four knee surgeries and hundreds of shots injected into my knee weekly to alleviate swelling and pain, my body is begging me to stop the pounding. My previous three surgeries were on my right knee. My most recent knee surgery took place this July and was on my left knee. After a few weeks of post-surgery recovery, I tried to go through all the necessary steps to get back on the court. While I've come back from surgery in the past, this time it felt different. One of my goals was to recover as fast as I could in order to be ready for the first WTA tournament in my hometown of Wuhan. As hard as I tried to get back to being 100%, my body kept telling me that, at 32, I will not be able to compete at the top level ever again. The sport is just too competitive, too good, to not be 100%.

Winning a Grand Slam title this year and achieving a ranking of World No.2 is the way I would like to leave competitive tennis. As hard as it's been to come to this decision, I am at peace with it. I have no regrets. I wasn't supposed to be here in the first place, remember? Not many people believed in my talent and my abilities, yet I found a way to persevere, to prove them (and sometimes myself!) wrong.

I've succeeded on the global stage in a sport that a few years ago was in its infancy in China. What I've accomplished for myself is beyond my wildest dreams. What I accomplished for my country is one of my most proud achievements.

In 2008, there were two professional women's tennis tournaments in China. Today, there are 10, one of them in Wuhan, my hometown. That to me is extraordinary! Serena Williams, Maria Sharapova and Venus Williams - with thirty Grand Slam singles titles among them - are coming to my hometown to play tennis for the fans of China! Just as I didn't think I could ever be a Grand Slam champion, never in my wildest dreams did I imagine that some of the best female athletes in the world could play tennis in Wuhan, in my backyard.

My contributions to the growth of the sport in China are very special to me. But I don't want to stop here. Together with IMG, my management company, we are putting together various plans on how we will continue to grow the sport of tennis in China. These plans include opening the Li Na Tennis Academy, which will provide scholarships for the future generation of Chinese tennis stars. I will also stay involved in the Right to Play, an organization dedicated to helping underprivileged children overcome challenges through sport. My philanthropic work will expand in scope as I continue to dedicate myself to helping those in need. What was once just a dream in China today is a reality.

On a personal side, I look forward to starting a new chapter of my life, hopefully having a family and reconnecting with those I did not have the luxury of spending a lot of time with while playing. I can't wait to revisit all the amazing places I played tennis in and see the world through a new set of eyes. I look forward to slowing down and living my life at a new, slower, relaxed pace.

Tennis is an individual sport and as players, our job is to spend a lot of time focusing on ourselves. But no player can ever become a champion alone and nobody knows this better than me. There isn't enough space here to thank everyone who has travelled on my journey with me and contributed to my success. But I must thank those that have stuck with me through the highs and the lows and have helped me become the person that I am today.

Thank you to:

My mother - for your never-ending support. Through the laughs and the tears, you've always been there for me.

My father - you were taken away from me way too early and I haven't been the same since. You've remained the sunshine in my life and I am who I am because of you.

Jiang Shan - you've been by my side for 20 years. You are my everything and I am grateful to have shared my life with you.

My first coaches Ms. Xia Xiyao and Ms. Yu Liqiao - for putting me on the tennis path.

Madame Sun and the Chinese Tennis Association - thank you for being trailblazers for tennis in China.

Mr. Hu Dechun and the Hubei Sports Bureau - for understanding me and supporting me through the years.

Women's Tennis Association - for your passion for women's tennis and hard work growing it around the world.

Mr. Chan Hongchang - for supporting me when I first decided to become a professional tennis player in 2008. You helped me make up my mind.

Thomas Hogstedt - for introducing me to professional tennis.

Michael Mortenson - for helping me win my first Grand Slam.

Carlos Rodriguez - for pushing me beyond the limits I thought I could reach.

Alex Stober - for taking care of me all of these years and pulling me together when I was falling apart.

Erich Rembeck and Johannes Wieber - for finding a way to make me pain free, over and over again.

Fred Zhang and the Nike team - you've been my guiding light, my support system and my biggest cheerleader. I will never forget it.

To Max Eisenbud and the entire IMG Team - for being the best management company in the world and for taking care of me every day.

To all the sponsors that have supported me through every stage of my career.

To my relatives, friends, and everyone who has helped me throughout my career - for always being there for me and for your never-ending support.

To my fellow tennis players - for being a part of my journey all of these years. I have so much respect for all of you.

To everyone in the media who's covered my career and helped the growth of tennis in China and around the world.

To the amazing tennis fans around the world - for your unyielding support of our sport and for playing every tennis match along with me.

And lastly, to tennis fans in China - for getting on the bandwagon and staying on it! I am grateful to each and every one of you for pushing me to be my best, embracing me and loving me unconditionally. There is no limit to how far we can take the sport of tennis in China, together.

When I started playing tennis, I was just a neighbourhood kid with an afterschool hobby, not realizing what magical journey lay ahead of me. If I only knew what a vehicle the sport of tennis, along with my success, would become for my beloved China. While my journey hasn't been easy, it has been rewarding. I've seen change happening in front of my eyes, young girls picking up tennis racquets, setting goals, following their hearts and believing in themselves. I hope that I've had the opportunity to inspire young women all over China to believe in themselves, to set their goals high and pursue them with vengeance and self-belief.

Whether you want to be a tennis player, a doctor, a lawyer, a teacher or a business leader, I urge you to believe in yourself and follow your dream. If I could do it, you can too! Be the bird that sticks out. With hard work, your dreams will come true.