Jessica Ennis-Hill has fallen from fourth to eighth place after six events at the Hypo-Meeting in Gotzis.
The Olympic champion, 29, was third overall at the end of a promising first day - traditionally her strongest - with a score of 3,928 points.
On Sunday she leapt a respectable 6.16m in the long jump but threw a disappointing 42.60m in the javelin.
With the 800m remaining, she has 5,544 points, still on course for the 6,200 needed to qualify for the Rio Olympics.
Ennis-Hill is competing in her first heptathlon since winning gold at London 2012.
A top-12 finish and score of 6,075 points would also secure qualification for this summer's World Championships.
Canada's Commonwealth champion and world silver medallist Brianne Theisen-Eaton leads ahead of the final event, remarkably achieving three personal bests on her way to a 5,834 score.
|Who needs what for 2015 World Championships?|
|Britain can send up to three heptathletes to Beijing in August. To achieve automatic selection, they need a top-12 finish in Gotzis, to be one of the first two Britons there (only two are competing) and to have achieved the 6,075-points qualification standard within the qualifying period.|
|Jessica Ennis-Hill needs to finish in the top 12 in Gotzis and score 6,075 points.|
|Katarina Johnson-Thompson already has the qualification standard, and though not competing in Gotzis, will expect to be selected anyway.|
|Morgan Lake also has the standard and will be an automatic pick if she finishes in the top 12 in Gotzis.|
Follow latest updates and reports on the second day of the Gotzis Hypo-Meeting on the BBC Sport website on Sunday, 31 May.