In February 2016, Gustavo was loaned to K League Challenge side Daejeon Citizen for the 2016 season.
[4] Gustavo made a debut on 21 September during the 1-3 away victory in the 1/16 final of the Bulgarian Cup against Lokomotiv Gorna Oryahovitsa.
[6] On 11 May 2018 Gustavo had a controversial performance during the 2-1 win over Beroe Stara Zagora.
He assisted for the first goal of João Paulo da Silva Araújo but later on was sent off for committing a brutal foul against Matheus Leoni.
[7] After a long goal-drought, on 25 August 2018, Gustavo scored in the last minute for the 0-2 away win over FC Vitosha Bistritsa.