Shericka Jackson, Williams-Mills rested for 4x400m relay heats
Women's 400m bronze medallist Shericka Jackson and veteran Novlene Williams-Mills will get the morning off as Jamaica's team competes in the women's 4x400m heats.
Jackson who claimed the bronze medal in a personal best 49.99, has been replaced in the relay line-up for the heat by the experienced Annastasia Le-Roy.
Chrisann Gordon comes in for Williams-Mills.
The 400m finalists Stephenie-Ann McPherson and Christine Day will however be on track for the heats to help Jamaica secure qualification to the medal round.
Jackson and Williams-Mills are expected to join Day and McPherson for the final, where the Jamaicans will be expecting to challenge for a medal.