Three-time gold medallist Ben Ainslie could only finish Monday's first Finn race in sixth place as Denmark's Jonas Hogh-Christensen proved he was no one-day wonder.
The 35-year-old Brit has been sluggish out of the blocks at previous Olympics but got off to a decent start yesterday, collecting two second places.
Hogh-Christensen was the victor in both races and impressed again on Monday, finishing second to New Zealand's Dan Slater in Weymouth Bay.
Ainslie, meanwhile, had to settle for sixth place after a difficult start.
The gold medal favourite had been close to Hogh-Christensen but lost ground upwind as he finished behind the Dane for a third successive race.