Isabelle Joschke, the leading woman in the Vendee Globe, was forced to quit the race on Saturday after damage to the keel of her boat MACSF, race organisers said.
The Franco-German sailor had rounded Cape Horn and was running 11th, 758 nautical miles (1,220 kilometres) behind leader Yannick Bestaven in the South Atlantic, when she noticed that her keel, which she had repaired on January 3, was no longer centred.
"It is obvious that Isabelle can no longer continue with her Vendee Globe and will have to retire," said her team manager Alain Gautier.
She became the seventh of the 33 starters to retire.
Gauthier said Joschke had lowered her sails but was sailing in the direction of a worsening depression with wind speeds of up to 35 knots.
He said he believed a forecast change of wind direction overnight "should allow her to escape to the north-east to escape this low pressure, and flatter seas should make things easier".
Further north, Bestaven in Maitre Coq IV was almost becalmed off the coast of Brazil as his closest pursuers, who had found a corridor of wind, cut into his lead.
By 2100 GMT, Charlie Dalin, who had been more than 420 nautical miles behind just two days earlier, gained another 70 nm in just six hours and had cut the gap to 176.8 nm in Apivia.
Thomas Ruyant in LinkedOut was also gaining and was 246.4 nm behind Bestaven.