Two years ago, a US quartet demoralised the field in the women's 4x400m, winning by nearly six seconds in a world-leading 3:19.02, the fastest time in the world since the 2012 Olympic Games held on the same London Stadium track. That performance produced, by far, the largest winning margin in the event at a World Championships. Although they may not be fielding as powerful a squad this time around, the USA still arrives in the Qatari capital poised to win a ninth title in the event.
Attracting the bulk of the attention on the championships' closing day will be Allyson Felix, the most decorated athlete in IAAF World Championships history, who will be looking to add a 17th medal to her collection, joining the 11 gold, three silver and two bronze that already pack her trophy case.
Felix has been working her way back from a year off for maternity leave this season, finishing an admirable sixth in the 400m at the always-competitive US Championships to earn herself a ticket to Doha as a member of the relay squad. She has since improved her season's best to 51.36 and arrives on the heels of a victory at the Skolimowska Memorial in Chorzow, Poland.
She's part of a pool that includes defending 400m and 4x400m champion Phyllis Francis, Kendall Ellis, Wadeline Jonathas, Courtney Okolo and national 400m champion Shakima Wimbley who've all clocked faster than 51 over one lap this season, so logic would dictate that they'll be in form to run well under their 3:24.04 qualification performance that leads this year's world list. Considering that mark – also a pending world U20 record – was set by a US quartet that won the Pan-American U20 title, it would be a bit embarrassing that a senior squad in Doha wouldn't.
The USA has won five of the past six world titles. Jamaica, who took top honours in 2015 to halt a US win streak at four, arrives with strong medal ambitions of their own as they aim to improve on their runner-up position of two years ago. The Caribbean island nation's pool includes Shericka Jackson, one of just four women to have run under 50 seconds this year, and sub-51 runners Stephenie Ann McPherson and Anastasia Le-Roy.
Poland also arrives with a point to prove. A perennial continental powerhouse in the event, a quartet from the northern European nation finally claimed its first World Championships medal two years ago when taking bronze behind the US and Great Britain & Northern Ireland. They're arguably even stronger now, arriving as the reigning European and IAAF World Relays champions. This year only a US squad has run faster than their 3:24.81 season's best. European 400m champion Justyna Swięty-Ersetic and Iga Baumgart-Witan, at 50.85 and 51.12, are the team's quickest this year.
Canada, Great Britain & Northern Ireland and Italy should also be in the medal hunt. Canada was a surprise fourth at the IAAF World Relays and later went on to clock 3:27.12 to take silver at the Pan-American Games while Italy edged a British quartet to take third in Yokohama. Great Britain & Northern Ireland returned the favour at the European Team Championships, edging the Italian squad by 0.20 in 3:27.12 to finish second, season's bests for both.
Nigeria, the African Games champions, could also be a factor.
Bob Ramsak for the IAAF