Olympic Heptathlon champion Jessica Ennis-Hill is a major doubt for the World Athletics Championships in August after withdrawing from the British Championships in Birmingham this weekend with an Achillies tendon problem.
Ennis-Hill is still to compete this season but coach Toni Minichiello remains confident the 27 year old will be available to participate in Moscow next month as she seeks to regain her world title.
The Brit is undergoing continual rehabilitation ahead of her return, but British Athletics are yet to confirm the full extent of the injury.
"She is following a very comprehensive rehabilitation programme, working with the British Athletics medical team and her physiotherapist Alison Rose," a BA statement read.
The 2009 world champion later tweeted: "Frustrating times! But I've not given up yet! #partofbeinganathlete."
Having already pulled out of the Women's Athletic Meeting in Edinburgh, the Diamond League 100m hurdles and the European Cup combined Events Super League meeting in Estonia, her home championships represents Ennis-Hill's latest withdrawal.
Should Ennis-Hill recover in time to compete then she will earn qualification automatically having already gained the 'A' qualifying standard but will travel to Russia as an outsider with limited warm-up time prior to the event.
Tatyana Chernova, the reigning world champion, is the current Heptathlon No.1 and will go into the World Championships as favourite ahead Ennis-Hill.