The British rider, who finished third at the 2020 race, was leading EF Education-Nippo during this year's race but pulled out shortly after the riders crested the third climb of stage 7, Puerto de Tudons, just past the mid-point of the day.
It's not yet known whether Carthy is ill or injured but the 27-year-old lost 2:50 on stage 6's uphill finish in Cullera after struggling mightily in the final kilometres of Thursday's stage, won by teammate Magnus Cort.
Carthy had come into the race among the major GC favourites after his podium spot last year. Earlier this season he finished fifth at the Tour of the Alps before riding to eighth overall at the Giro d'Italia.
He came into the Vuelta in good form, having won the final stage of the Vuelta a Burgos at the summit finish of Lagunas de Neila, despite finishing 41st overall.
EF Education-Nippo's best-placed rider on the general classification is now fellow Briton Simon Carr, who joined the team from Delko this season. He lies in 23rd place at 2:53 behind race leader Primož Roglič (Jumbo-Visma).
Daniel joined Cyclingnews as staff writer in 2019 after working as a freelancer around pro cycling media for the previous seven years.
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