Keely Hodgkinson pulled out off the 400m final at the UK Athletics Championships as a precaution, Sky Sports News understands.
The 800m Olympic champion has been competing over the short distance in a bid to improve her first-lap speed and challenge the 800m record later this summer, after breaking the indoor world record with a time of 1:54.87 in France earlier this year.
Hodgkinson, 24, qualified from the heats on Saturday but pulled out from the final moments before it was due to start. She looked emotional as she stood at the side of the track in Birmingham.
- Hodgkinson targets 800m world record
- Not got Sky? Get Sky Sports or stream with no contract on NOW
- Download the Sky Sports app
Sky Sports News has been told by her coach Trevor Painter that "all is fine, bit of tightness and decided not to risk it".
It is understood that Hodgkinson felt anxious during the warm-up and on the start-line before deciding to withdraw and avoid long-term injury, after suffering from several hamstring injuries last year.
The move is understood to be precautionary, given her main aim of the season is to win the 800m race at the European Championships and to try an break the record in London on July 18.
Hodgkinson said: "I wasn't feeling 100 per cent standing on the start-line, so I made the tough decision to step away and not race.
"I didn't want to risk anything this summer."
The 800m world record of 1:53.28 was set by Czech Jarmila Kratochvilova 43 years ago.
Team GB's Amber Anning - after Hodgkinson's withdrawal - ultimately defended her 400m title on a Father's Day rife with successes for British dads.
Olympic silver 400m medallist Matthew Hudson-Smith was given an exemption last year so he could support his wife through the challenging birth of their now healthy daughter Eden.
The local favourite, a Wolves academy product in his youth, reclaimed his 400m title in 44.45secs to secure his place at August's European Championships at the same venue.
First-time dad Alastair Chalmers, who welcomed a baby boy on Tuesday, was the 400m hurdles champion and 200m champion Zharnel Hughes revealed his agent had texted him before Saturday's 100m final to say "do this one for your son".
Scotland's Jake Wightman, the 2022 world gold and 2025 world silver 1500m medallist, was among Sunday's other champions, winning the men's 800m final in 1:45.40.
Success Eduan beat Amy Hunt, who defended her 100m title on Saturday, to win the women's 200m in a personal best 22.43.
(c) Sky Sports 2026: Keely Hodgkinson: Olympic gold medalist pulls out of UK Athletics Championships 400m final as precaution

World Cup 2026: Spain show why they are favourites as Lamine Yamal inspires statement win over Saudi Arabia
New Zealand thrash England by 253 runs as Matt Henry takes 11-wicket haul at The Oval to level three-match series
Lucas Bergvall transfer news: Tottenham midfielder asks to leave Premier League club in search for first-team football
England vs New Zealand, second Test player ratings: Joe Root's class endures as debutants struggle at Oval