Sérgio Santos

tes Iquique
In 2014, Santos began exploring professional options in Chile. After trying negotiations with Palestino and Magallanes, he signed with Audax Italiano. In August 2018, Santos signed a contract extension with Italiano through mid-2020. Santos scored nine goals in 16 league appearances during the 2018 season for Audax and was the club's leading scorer. He helped the club qualify for the 2018 Copa Sudamericana and reach the Copa Chile final, where the side finished as runners-up to Palestino.

Philadelphia Union
On 14 December 2018, signed with Philadelphia Union competing in Major League Soccer. The signing was completed for approximately $500,000 transfer fee and as a TAM-level player. After a slow start due to injuries, Santos scored his first two goals for the Union on May 5 versus New England Revolution in a 6–1 victory. Santos would finish his first season with four goals and one assist.

While the 2020 season was disrupted by COVID-19 pandemic, Santos found his footing with the Union scoring the first goal of the season against Los Angeles FC. In October during a top of the table match-up, Santos scored his first professional hat trick against Toronto FC (the fourth in Union history); earning him MLS Player of the Week honors. The season would end with the Union earning their first trophy in club history, the 2020 Supporters' Shield, leading the team with eight goals.