Honda's six-time MotoGP champion Marc Marquez will not race at the Indonesia Grand Prix later on Sunday after being ruled unfit due to a concussion following a crash during the warm-up session, organisers said.

Marquez suffered a shocking highside on turn seven and was visibly dazed after landing heavily on his left side and taking a whack to his head. Hospital checks subsequently revealed the Spaniard had suffered a concussion.

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The 29-year-old had already crashed twice during qualifying on Saturday. He was due to start from 14th on the grid after moving up a spot following Franco Morbidelli's three-place grid penalty.

Organisers said on Sunday the race would be reduced from 27 laps to 20 due to tyre safety concerns caused by extreme heat at the Mandalika track. The race start was then delayed due to torrential rain.

Reigning world champion Fabio Quartararo will start from pole in Indonesia's first MotoGP race since 1997.