The biggest storyline entering the 2016 Olympics in Rio may be Simone Biles, the three time all-around World Champion who dominated the field once again in Glasgow to retain her crown as the undisputed "Queen Of Gymnastics". If she wins the gold, she will be discussed as, potentially, the greatest women's gymnast of all time, and given her excellence in almost every apparatus, she is certainly the heavy favorite to win to walk out of Rio as an Olympic champion.

Perhaps the only woman who could beat her also happens to be her team mate...and the last woman to be named Olympic champion. 

Gabby Douglas would have been forgiven if she decided to walk away from gymnastics after winning the all-around gold medal in London. After all, that's what most gymnasts do. Why go through another four years of hard work and training for something you've already accomplished? You already accomplished your biggest goal in life. What more do you have to prove?

For Douglas, it wasn't about what she accomplished. It's about doing something that hasn't been done in 50 years. It's about repeating as champion, a task most claim is impossible.

When people say I can’t do something, I love it,” Douglas said in an interview with the Associated Press back in June. “I just say, ‘all right, let’s go. Let’s get it.’ I’m more confident. More courageous. More warrior-minded.”

Douglas wants to go for history, which is hard enough, but she's doing so in the middle of Biles' historic run. Biles was too young to make the Olympic team back in 2012, but when most of the Fierce Five from London took time off following their gold medal run in London, Biles stepped up to the plate. She has won ten gold medals in three World Championships, making her the most decorated female gymnast of all time. She is the best in the world on the floor exercise and the balance beam, and, if she nails a higher scoring second vault, she'll be the best in that apparatus, as well. It would take a monumental effort to defeat Biles.

Doing something unexpected, however, is how Douglas has gotten to where she is now. Entering the 2012 Olympics, all eyes were on reigning World Champion Jordyn Wieber, another one of Douglas' team mates. Wieber was expected to compete against the Russian duo of Viktoria Komova and Aliya Mustafina for the gold medal. Douglas, however, not only made qualification ahead of Wieber, but also took down the Russians to walk away with her first international individual gold medal. 

Douglas walked away with the all-around silver medal in Glasgow, becoming the first woman since 1981 to win an individual medal in a World Championships after winning the Olympic gold medal. She finished a full point behind Biles, however, and Biles was not flawless in her final. Still, Biles had been competing against the top competition in the world for the past three years, while Douglas was competing in her first major international event since London. Douglas is expected to improve as she puts in more time at the gym and competes in more competitions prior to Rio. 

The greatest part of this rivalry is that they are not only the best gymnasts in the world, but they are also team mates and good friends. The two will genuinely be proud of the other's success, while also using each other to improve. The battle for the gold in Rio is going to be a fierce one, which will be great for the sport of gymnastics and the fans watching the Olympics. Whoever walks out as the champion will truly have earned it.