Great Britain failed to reach the final of the mixed 4x400m relay on the opening day of the World Athletics Championships.
Joe Brier, Zoey Clark, Alex Haydock-Wilson and Laviai Nielsen clocked three minutes 14.75 seconds in Eugene on Friday.
It meant they finished sixth in their heat at Hayward Field, ninth fastest and out of any qualification positions.
Haydock-Wilson, who ran a poor third leg, said: “I take full accountability for that, huge sorry to the team, they ran their hearts out and trusted me to do my job and I’ll make sure next time I won’t let them down.
“I love having a lot to do and normally I would be able to rise to that challenge. Physically I think I just wasn’t ready and the rest of the team were.”
Nick Miller qualified for Saturday’s hammer final after coming ninth in pool A, throwing 77.13m.
“I’ve not been throwing very well all year so I adjusted for that and I’m throwing well so I just need to move back tomorrow,” he said. “I’ll do a little bit of lifting and then just rest, eat and sleep and come back tomorrow.
“It’s nice being in the middle of the stadium for once instead of kind of in a corner.
“I’m sure when we have the final it’s going to be a little bit louder and I’m looking forward to that. It’s been a little bit quiet in the last few years so hopefully this year it’ll be good.”
Joel Clarke-Khan was unable to make the high jump after only clearing 2.21m.
Later, Laura Muir opens her quest for a first World Championships medal in the 1500m with Zharnel Hughes and Reece Prescod running in the 100m heats and Holly Bradshaw in pole vault qualification.
