Britain's Zharnel Hughes has withdrawn from the men's 200-metre at the Paris Olympics due to hamstring tightness that will require 48 hours of monitoring, British Athletics said in a statement on Monday.
The British record holder in the event came sixth in his 100-metre semifinal on Sunday, a day before the 200-metre heats.
"No decision has been taken as yet in relation to his relay involvement," British Athletics said.
The heats of the men's 4x100 relay are on Thursday with the final scheduled for Friday.
Hughes, 29, was the bronze medallist in the 100-metre at last year's world championships and broke the national 100-metre and 200- metre records last year.