Pavel Maslak will face an uphill battle in his ambitions to become the first three-time 400m champion.
The Czech cruised to back-to-back titles in 2014 and 2016, winning both by fairly convincing margins, but hasn't exhibited quite the same pre-champs form this year. He's raced twice on the IAAF World Indoor Tour, finishing third in Madrid in 46.14 and second in Torun, clocking 46.17.
His season's best is more than a second shy of Bralon Taplin's 44.88 world lead, suggesting the 25-year-old Grenadian’s rise is set to continue this year. His breakout campaign came in 2016, a season which included a fourth place finish at the World Indoor Championships and seventh at the Olympic Games while improving to 44.38 outdoors. His 44.88 clocking in College Station, Texas, on 3 February was the sixth fastest indoor performance of all-time, marking him as the man to beat in Birmingham.
As usual, the USA comes armed with a solid contingent, with Michael Cherry and Aldrich Bailey carrying the torch this time for the traditional quarter-mile powerhouse. Cherry, 22, took the national title in the altitude of Albuquerque with a 45.53 lifetime best, the second fastest among Birmingham entrants. He also won his other race, clocking 46.46 to beat a strong field at New York's Millrose Games.
Bailey was quick in Albuquerque as well, winning his section in 45.59, the third fastest of those present this weekend. Like his teammate, Bailey, 24, has some major championships relay experience but will be making his first solo appearance on a large stage.
Trinidad and Tobago arrives well-armed with Deon Lendore, the bronze medallist at these championships two years ago. The 25-year-old has raced twice in 2018, clocking 45.85 in College Station on 3 February and 46.25 at the Tour stop in Boston, winning on both occasions.
Others to watch include Spaniard Oscar Husillos, who clocked a 45.86 national record in Madrid, Jamaican Javon Francis, who improved to 45.97 in Lubbock, Texas, earlier this month, and Slovenian record holder Luka Janezic, who arrives with victories in Vienna and Torun under his belt with a 46.02 best.
Qatar's Abdalelah Haroun, the silver medallist in Portland two years ago, also returns. The 21-year-old won the Asian indoor title in Tehran clocking 46.37, his only race of the year.
Bob Ramsak for the IAAF