Some of the most interesting stories heading into the 2017 IAAF World Track and Field Championships will span the globe, featuring names other than Usain Bolt and Allyson Felix. Here is a look at 10 compelling athletes eager for medals on track's biggest stage this year:
Abdul Hakim Sani Brown (Japan)
Event: 100 meters, 200
It's probable that Sani Brown is still a few years from medal contention. He's just entering his freshman year at Florida, but the recent high school grad has already shown he's ready for the world stage. He won the 100 and 200 titles at the 2015 IAAF World Youth Championships and was named IAAF Rising Star of the Year. In 2016, he was a good bet for Japan's Olympic team but had to withdraw from nationals with a thigh injury. Sani Brown qualified for London in June by winning the 100 in a personal-best time of 10.05 seconds, then won the 200 in 20.32, also a personal best. He's the first Japanese sprinter to sweep those events in 14 years. Sani Brown, whose mother (a former top high school hurdler) is from Japan and father from Ghana, has been training in the Netherlands in preparation for worlds and his first season at Florida. He says he has been focusing on weight training to become more explosive.
Prime number: No Japanese sprinter has ever broken 10 seconds in the 100. Sani Brown is just .05 seconds off Koji Ito's national record.
Quotable: "I'm very happy about being No. 1 in Japan, but I don't want to settle for this. I want to do well at the world championships and other competitions I've got ahead of me." -- Sani Brown
Wayde van Niekerk (South Africa)
Event: 100, 200, 400
Who's the next Bolt? Probably no one, but van Niekerk might be the closest. At the Rio Games, the slender former rugby player (6-foot, 159 pounds) set a world record in the 400 (43.03 seconds) in winning gold. That matched his victory in the same event at worlds in 2015. This year, he set personal bests in the 100 (9.94) and 200 (19.84) and broke Michael Johnson's world record in the seldom-run 300 (30.81). He's the only person to have run the 100 under 10 seconds, the 200 under 20 seconds and the 400 under 44 seconds. With Bolt retiring, the door is open for van Niekerk.
Prime number: He'll attempt to become just the second man to win the 200/400 double at the world championships. The United States' Johnson did it in 1995.
Quotable: "[He's] arguably the best sportsman to come out of South Africa" -- Marc Labuschagne, former South African sprint coach
Mo Farah (Great Britain)
Event: 5,000 and 10,000
The four-time Olympic champion has said this will be his last year running on the track before he transitions to road racing. It will be a surprise if anyone can stop him from adding to his collection of five world championship gold medals. Sir Mo Farah has won back-to-back 5,000 and 10,000 titles in the 2012-16 Olympics and 2013-15 world championships.
Prime number: It has been six years since Farah lost a 5,000 or 10,000 race in an Olympics or world championships. In 2011, he took silver in the 10,000 when he was passed by Ethiopia's Ibrahim Jeilan just yards from the finish.
Quotable: "One of the things I've always liked to be able to do is finish on a high. I've always wanted that. I will try my best, but it ain't going to be easy." -- Farah
Neeraj Chopra (India)
Chopra, the former world junior champion, is at the front of a surging Indian track and field program that recently dominated the 2017 Asian Track and Field Championships. Host India won 29 medals, and Chopra's gold in the javelin was one of 12 for the country. Now competing in his first year in the elite Diamond League, Chopra is quickly moving into the world's top ranks. His throw of 86.48 meters (283.72 feet) in 2016 is an Indian and junior world record. He ranks eighth in the world this year at 85.63 meters (280.93 feet). Chopra, the son of a farmer, originally took up track and field at the advice of an uncle to get in better shape. But he quickly showed his athleticism and an intelligence to grasp concepts and techniques.
Prime number: India has won just one medal in worlds history, a bronze.
Quotable: "He is very mature for his age. What stands out in Neeraj is his ability to absorb information and then enact it into his physical movements. At times, it's instantaneous." -- Chopra's coach, Garry Calvert
Hellen Obiri (Kenya)
Event: 1,500 and 5,000
Obiri is a corporal in the Kenya Defense Forces. She's the mother of a young daughter. And, she was a reluctant middle-distance runner. She ran the 200 and 400 in school and didn't take up longer distances until she was in the armed forces. Obiri's rise to elite status has been steady, however, with her only time off in 2015 for maternity leave. She won gold in the 3,000 at the 2012 world indoor championships, bronze in the 1,500 at the 2013 world championships and silver in the 5,000 at the Rio Games. Now, following the retirement of teammate Vivian Cheruiyot -- a four-time world champion in the 5,000 and 10,000 -- the door is open for Obiri. She recently ran 14:18.37 to break the Kenyan record in the 5,000 -- and beat her Olympic time by more than 11 seconds. In May, she finished second to countrywoman and Olympic champion Faith Chepngetich Kipyegon in the 1,500 at the Prefontaine Classic. In July, she smashed the Kenyan mile record (4:16.56) in London.
Prime number: Obiri's recent national record in the 5,000 is the fifth fastest in history.
Quotable: "I feel the weight on my shoulders after Vivian's exit. I feel the whole world has its eyes on me." -- Obiri
Sally Pearson (Australia)
Event: 100-meter hurdles
There were times in recent years Pearson wasn't sure she would ever make it back to elite status. Between 2008 and 2013, she ranked among the world's best, winning Olympic silver in 2008 and gold in 2012. But in 2015 she suffered a horrible injury to her left wrist -- called a "bone explosion" by doctors -- when she fell during a race in Rome. When she first saw the damage, she was shocked. "I thought they would have to amputate," she said. A year later, she was in the midst of a comeback and hoping to go to Rio, but tore a hamstring. Now, Pearson (formerly Sally McLellan) is headed back to the world championships, having won her eighth Australian championship in 12.53 seconds and following it with a 12.48 in a Diamond League meet in London. It's not as good as the Olympic record she set in 2008 (12.35), but it's her fastest time in five years.
Prime number: 12. That was the number of broken bones (plus a dislocation) she suffered in her wrist, hand and arm in 2015.
Quotable: "The biggest thing for me is I can be competitive now. I can push myself [against rivals]. That is what I'm really excited about." -- Pearson
Beth Potter (Great Britain)
In 2016, Potter made the 10,000 Olympic team, where she finished 34th in 32:03.45. Afterward, the former high school physics teacher from Scotland wanted a challenge, so she switched to triathlon with the intent of making the Olympic team for Tokyo in 2020. "I want to give it a crack for six to 12 months and see how I fare," she said in January. Five months later, however, Potter returned to the track to win her first national title in the 10,000 (32:04.63). It's just a quick detour from triathlon -- still her main focus -- but she believes she now has more endurance on the track, even though she's running fewer miles per week. In her first race back, she qualified for worlds.
Prime number: She's running about 50 miles per week now, roughly 13 fewer per week than when she was training only for the 10,000.
Quotable: "What I've been doing lately is obviously working. I'm getting my aerobic strength from other areas like the bike and pool and my legs are a bit fresher, so it's win-win." -- Potter, on competing in both triathlon and track
Dafne Schippers (Netherlands)
Event: 100, 200, 4x100 relay
Schippers was one of the world's best heptathletes. In 2013, she was a bronze medalist at the world championships. But because of all the stress on her knees from training and competing in so many events, she decided in 2015 to focus only on sprinting. Now, Schippers, a foodie who posts recipes and food reviews on her website's blog (dafnelikes.com), is thriving. She's being compared to Fanny Blankers-Koen, the great Dutch Olympic sprinter and hurdler. Schippers, "The Flying Dutchwoman," won gold in the 200 and silver in the 100 at worlds in 2015. At the 2016 Olympics, she was second in the 200 to Jamaican Elaine Thompson and fifth in the 100. In July, Schippers ran 22.10 in Switzerland to win a Diamond League 200 race, the fastest time in the world this year.
Prime number: Her 21.63 in the 200 in 2015 ranks as the third-best time ever, behind only Florence Griffith Joyner and Marion Jones.
Quotable: "Her style, her build ... she reminds me of my mother." -- Jan Blankers, on the comparison of Schippers to Fanny Blankers-Koen
Julius Yego (Kenya)
Kenya has earned its reputation as a bastion of long-distance runners. Now, Yego has earned acclaim for tackling long distances. Two years ago, in Beijing, Yego became the first Kenyan field athlete to win gold at the world championships. He then won silver at the Olympics in Brazil and has the sixth-best throw in the world this year. He has called himself "Mr. YouTube Man," as he has essentially coached himself to greatness by studying videos of great throwers to learn techniques. He grew up in a rural area with little coaching or money to attend international junior meets. His breakthrough came in 2011, when he became the first Kenyan to win a field event at the All-Africa Games. The following year at the London Olympics, he was the first Kenyan to make a javelin final.
Prime number: One. Yego was able to make just one throw at the Rio Games before withdrawing with an injury. But it stood up for the silver.
Quotable: "I have a passion for javelin throw. I think somewhere in my blood is written javelin." -- Yego