Francesco Bagnaia wins Algarve MotoGP after champion Fabio Quartararo falls

Ducati rider Francesco Bagnaia won a red-flagged Algarve MotoGP on Sunday as newly-crowned world champion Fabio Quartararo failed to finish after falling off his Yamaha.Italy's Bagnaia, who had started on pole position for a fifth consecutive race, finished ahead of 2020 world champion Joan Mir of Suzuki and Australia's Jack Miller, also on a Ducati.Starting from a lowly seventh on the grid, Quartararo fell five laps from the end of the race on the same circuit where he had won the Portuguese MotoGP in April.In a dramatic race, Bagnaia claimed his third win of the season, handing Ducati the constructors title.The race ended prematurely under red flags, however, after Iker Lecuona and Miguel Oliveira, both on KTM bikes, crashed two laps from home.Both riders were conscious although Oliveira required a check-up at the circuit medical centre.With just one race left this season in Valencia next weekend, Bagnaia and Mir are guaranteed to finish second and third in the championship.In front of a crowd of around 28,000 spectators, seven-time MotoGP world champion Valentino Rossi finished in 13th place in the penultimate race of his career. The 42-year-old will ride off into retirement next week.Spanish rider Pedro Acosta won the Moto3 world title at the age of 17 on Sunday, marking himself out as a name to watch after triumphing in the Algarve race.Acosta won six of 17 races in a spectacular debut season at this level and took the flag in Portugal after the fall of Italian rider Dennis Foggia, the only rival who had a chance of beating him to the title.At 17 days and 166 days, KTM rider Acosta becomes the second youngest world champion in any Moto category behind only Loris Capirossi of Italy, who keeps his record by a single day.Six-time MotoGP world champion Marc Marquez -- himself the youngest ever MotoGP champion when he won his first aged 20 -- has already earmarked his fellow Spaniard for greatness."He will soon move up to MotoGP and when he does, if he continues like this, he will make things very difficult," Marquez predicted at the start of the season.