Sidnei was used intermittently during his first season in Portugal, but still managed to appear in 24 Primeira Liga games and score three goals in as many wins, including the 2–0 derby home win against Sporting Clube de Portugal on 27 September 2008. In November, Benfica bought another 50% of his rights for €2 million, and GestiFute acquired the rights to receive 30% from any future transfer. He played in only five league matches during the following campaign – ten overall appearances – as the club won the national championship after a five-year wait. After spending the first half of 2010–11 on the bench, Sidnei was propelled to the starting XI after David Luiz moved to Chelsea in the winter transfer window. On 21 February 2011, he was sent off in a league game at Sporting but his team still managed to win it 2–0 and, late into the following month, he renewed his contract for a further three seasons until 2016; however, due to poor performances, he lost his starting place to Jardel. In early June 2011, Beşiktaş J.K. agreed with Benfica on a one-year loan, with the option to make the move permanent. On 19 September he scored a brace for the first in his career, helping to a 3–1 Süper Lig home win over MKE Ankaragücü. As the Turkish club opted against exercising its option, Sidnei returned to Portugal and found himself demoted to the B-team. On 29 July 2013, he and Pizzi were loaned to La Liga's RCD Espanyol on a one-year deal.
Deportivo
On 1 September 2014, Sidnei moved to fellow league side Deportivo de La Coruña also on loan. After appearing in 32 matches to help his team avoid relegation, his loan was extended for a further year. Sidnei had a contract running until 2018, with the Galicians sharing his rights with Benfica and GestiFute. He scored his first goal in the Spanish top division on 5 December 2016, helping the hosts rout Real Sociedad 5–1. On 19 July 2018, Deportivo announced they had reached an agreement with FC Krasnodar over the transfer of Sidnei. The transfer was called off two days later, however, with the player having been unable to agree terms.
Betis
In August 2018, Sidnei joined Real Betis also from the Spanish top flight on a four-year contract.
