César Joel Valencia Castillo (born 16 November 1994) is an Ecuadorian professional footballer who plays as a winger for Polish club Zagłębie Sosnowiec.

[4] Valencia made his only senior appearance for the club as a substitute for Pablo Barrera late in a 6–0 La Liga defeat to Real Madrid on 28 August 2011.

[5] He spent much of the following three years in the reserve team and on loan at Málaga B,[6][7] before departing La Romareda to join Segunda División B club Logroñés in August 2014.

[citation needed] He made 28 appearances and scored two goals during 18 months at the Bonifika Stadium,[4] before departing to join Polish Ekstraklasa club Piast Gliwice in August 2017, one a one-year contract, with a three-year option.

[17] Valencia played much of the remaining three years of his contract away on loan and Brentford's promotion to the Premier League at the end of the 2020–21 season pushed him further down the pecking order.