Wiegersma finished second at Badminton on Shaabrak
Lucy Wiegersma has become the second member of Britain's Olympic eventing team to withdraw from the Games.
Her horse, Shaabrak, suffered a minor setback during training, costing Wiegersma her place in Beijing.
In June, Zara Phillips was also forced to pull out after her horse, Toytown, suffered an injury.
The British Olympic Association has announced that their places will be taken by Daisy Dick, riding Spring Along, and Tina Cook on Miners Frolic.
Simon Clegg, Team GB 2008 Chef de Mission, said: "While we are naturally disappointed for Zara and Lucy, we are fortunate enough to have incredibly talented and experienced riders to step in to the fold."
Cook added: "I am elated to be chosen, but someone's happiness is another's sadness.
"I have been in that position before and was convinced after Atlanta and Sydney that I wouldn't get another chance."