[2] He subsequently signed a contract with the club, and made his senior debut on 8 August 2017 by starting in a 1–1 away draw against Presidente Prudente FC for the Campeonato Paulista Segunda Divisão championship.

[4] He made his debut for the club on 3 February 2018, coming on as a second-half substitute in a 1–1 Campeonato Paulista home draw against Ponte Preta.

[5] Júnior Santos scored his first professional goal on 26 February 2018, netting the game's only in a home defeat of Red Bull Brasil.

On 8 April 2018, Júnior Santos was loaned to Série B side Ponte Preta until the end of the year, with a buyout clause.

On 26 June 2019, Júnior Santos moved abroad for the first time in his career, after signing for J2 League side Kashiwa Reysol.