Jo Pavey and Louise Damen have pulled out of the UK marathon team for next month's World Championships.
Pavey, 37, has withdrawn due to a minor foot injury which has forced her to ease off training for three to four weeks.
Damen, 28, is suffering from a sports hernia and has dropped out in order to focus on her 2012 preparations.
Mara Yamauchi, Alyson Dixon and Susan Partridge will now make up the GB team in Daegu, South Korea.
Pavey made her debut over marathon distance in London in April and her time of two hours 28 minutes 24 seconds was enough to qualify her for both Daegu and next year's London Olympics.
The 2006 Commonwealth Games 5,000m silver medallist has struggled with injury since having a break to give birth to her son Jacob, missing last year's European Championships and Commonwealth Games due to a stress fracture in her foot.
Pavey has been in good form this year though, adding success in the Bupa London 10,000 - where she saw off the challenge of the returning Paula Radcliffe - to her impressive effort in the London Marathon.