Learn about the top storylines for the women's 800m at the IAAF World Championships in London in the event preview. 

When: 
August 10, 1:35 PM CT (heats)
August 11, 1:35 PM CT (semi-finals)
August 13, 1:10 PM CT (final)

Top International Contenders: Caster Semenya (South Africa), Francine Niyonsaba (Burundi), Margaret Wambui (Kenya), Melissa Bishop (Canada), Eunice Sum (Kenya)

Team USA: Ajee Wilson, Charlene Lipsey, Brenda Martinez

2016 Olympic 800m Final: 

Place	Athlete	Country	Time	Back In 2017?
1	Caster Semenya	RSA	1:55.28	YES
2	Francine Niyonsaba	BDI	1:56.49	YES
3	Margaret Wambui	KEN	1:56.89	YES
4	Melissa Bishop	CAN	1:57.02	YES
5	Joanna Jóźwik	POL	1:57.37	YES
6	Lynsey Sharp	GBR	1:57.69	YES
7	Maryna Arzamasova	BLR	1:59.10	YES
8	Kate Grace	USA	1:59.57	YES, but 1500m only

Analysis: If you had asked me three weeks ago who would be on the podium for the women's 800m, I would have told you it will be Rio 2016 the sequel, meaning Caster Semenya, Francine Niyonsaba, and Margaret Wambui would crush everyone once again. But the Monaco Diamond League race changed everything. 

This year started with the top three dominating nearly every Diamond League competition in the London World Championship build-up. Semenya would win and some combination of Niyonsaba or Wambui would finish second and third. This trend continued until Monaco when Ajee Wilson stepped up and challenged the favorites. 



Semenya still won and lowered her own South African national record to 1:55.27, which beat her previous lifetime best from winning the 2016 Olympic Games. Niyonsaba followed for second in 1:55.47, but Wilson pushed both competitors through the line to finish third in an American record of 1:55.61. All three women broke their respective national records and set lifetime bests. But Wilson's performance was especially significant for a number of reasons. 

Wilson became the first American woman in history to break the 1:56 barrier. Her performance shattered Jearl Miles Clark's 1:56.40 national record set in 1999 and improved upon her own lifetime best by a whopping two seconds. Even more telling was Wilson's racing style against the best middle distance runners in the world. She ran with Semenya and Niyonsaba for the entire race and even challenged the two superstars down the homestretch. Top-three mainstay Wambui was nowhere in sight as she finished a distant ninth. 

Prior to Monaco, Wilson showed signs of a breakthrough at the USATF Outdoor Championships when she made her fourth senior world championship team by throwing down a dominant victory in the 800m final. She won the national title in 1:57.78 by negative splitting. In the same race, her training partner Charlene Lipsey finished second in a personal best of 1:58.01. The performance marked her first time qualifying for a world championship team and highlighted a season of breakthroughs that began during indoors. Behind Wilson and Lipsey, Brenda Martinez finished third in a season's best of 1:58.46 to make her fourth international team. The 2013 world silver medalist also competed in the Monaco race where she lowered her season's best to 1:58.43. 



Semenya is still considered the heavy favorite to repeat. She hasn't lost an 800m race in two years and is already running faster than she did to win her second Olympic gold medal last summer. The wildcard with Semenya will be if she chooses to double and run the 1500m as well as the 800m. She entered herself in the double -- as announced by Athletics South Africa on Tuesday -- but she was also rumored to compete the 400/800m double last year in Rio and opted to focus on the latter. If Semenya does run the 1500m, she will have a tough racing schedule. The 1500m final is August 7 and the first round of the 800m begins on August 10. 

Niyonsaba has also been on a roll. Prior to Monaco, she ran a season's best of 1:56.82 to win the Lausanne Diamond League meeting. The Oregon Track Club standout shattered her lifetime best in Monaco when she ran 1:55.47 on the heels of Semenya. 

Pior to Monaco, Wambui was looking strong. The Olympic bronze medalist opened the season with a still-standing season's best of 1:57.03 in Doha and captured two more top three finishes in Diamond League competition. But Monaco was a hard wake-up call for the Kenyan. She faded to last place in 2:02.13, the slowest race of the season aside from her 2:04 run from the semifinal of the Kenyan national championships. If she returns to the same form that earned her Olympic bronze, she will be a force in London. 

As mentioned earlier, Wilson's breakthrough performance in Monaco was a game changer. She proved that the seemingly unstoppable trio can not only be broken up, but challenged down the line.