The 21-year-old Brazilian centre-back made his first-team breakthrough under Luis Enrique last season with a pair of La Liga starts and a substitute appearance in the Champions League.
Barcelona 13/2 to win CL
Barca tweeted on Tuesday to confirm Marlon had been excused from training with Ernesto Valverde’s squad in order to complete a transfer to Nice.
Lucien Favre’s side secured a third-place finish in Ligue 1 last season but they have started the current campaign poorly.
Napoli beat them 4-0 on aggregate in the Champions League play-off round, while they have lost three from four in France’s top flight.
