Boxing has become one of the Olympics' most popular sports, and the Tokyo Games is sure to offer yet another compelling set of storylines to keep up with for one of the world's oldest pastimes. This year, though, some of the most recognizable names in the sport will be unable to participate due to going pro or because of injury.

Pat McCormack will be returning to the ring for Great Britain this summer. McCormack was unable to take home a medal at the Rio Games, but the 25-year-old (he turns 26 in June) is expected by many to take a big step forward in Tokyo. McCormack won silver at the 2019 AIBA World Boxing Championships and won gold at the 2019 European Games.

Shakhobidin Zoirov is also expected to return for the Olympics this summer. Zoirov won gold in the flyweight class at the Rio Games, and now the 28-year-old hopes to defend his title against some of the up-and-coming flyweight competitors.

The United States will be missing one of its most dominant Olympians when boxing at the Tokyo Games begins. Claressa Shields, the two-time gold medalist in the middleweight class, opted to go pro after winning her second consecutive gold medal at the Rio Games. Unlike in other sports, professional boxers are not allowed to represent the United States in the Olympics. And since Shields has now gone pro, she is ineligible to compete.

Legendary British boxer Nicola Adams will also not return for the Tokyo Games after announcing her retirement in 2019 due to an injury to her eye. Adams, 38, became the first female boxer to win an Olympic title at the London Games in 2012 and in 2016 became the first female boxer to win two consecutive golds.

Justis Huni is only 21, but the 6-foot-4 behemoth certainly doesn't look it. He will also be one of the few professional boxers competing at the Tokyo Games. Huni won bronze at the 2019 AIBA World Boxing Championships as a super heavyweight and will look to put Australian boxing on the map by winning the country's first ever Olympic gold medal in boxing.

France's Billal Bennama is also expected to make some noise in Tokyo. The 22-year-old (he turns 23 just before the Tokyo Games) took home a bronze medal at the 2019 AIBA World Boxing Championships as a flyweight and could be gunning for the aforementioned Shakhobidin Zoirov in the 52 kilogram weight class.