"It's obviously something I've pictured in my mind, to come in and play a similar role to him," Johnson said about the Starc comparisons. "There were a few nerves there, and obviously big shoes to ...

Firing on all burners, Johnson, wearing customized, symbolically gold-colored track shoes, set an Olympic record of 43.49 in winning the 400 on July 29. Three days later came the 200 finals.

Johnson's own partnership with Under Armour dates back to 2015, when he signed a "long-term" contract to team up on an apparel and footwear brand. Like Stack, Johnson has voiced his own concerns ...