Sebastián Viera

Born in Florida, Florida Department, Viera started his professional career with Club Nacional de Football, notably winning the 2005 Uruguayan Primera División without losing a single match. After three seasons, he was expected to move to Premier League club Arsenal in August 2005, but its manager Arsène Wenger withdrew from the deal when the player did not pass his medical. Eventually, Viera signed with Villarreal CF in Spain, moving alongside Mariano Barbosa (also a goalkeeper) on a four-year contract. He would be an undisputed starter the following two seasons, although he missed both legs of the 2005–06 UEFA Champions League semi-finals against Arsenal. Viera eventually lost his job midway through the 2007–08 campaign to newly signed Diego López, and never regained it again – no La Liga games in 2008–09 – being released in July 2009. On 7 December he signed a one-and-a-half-year contract with Greek side Athlitiki Enosi Larissa FC, being made eligible to play however only in January 2010; his contract was terminated in December. In April 2011, Viera joined Atlético Junior, remaining in Colombia until his retirement aged 40. He won seven trophies during his 12-year spell in Barranquilla, including three Categoría Primera A championships. In 2020, Viera was voted the second-most important player in Junior's history in a poll conducted by the website La Cháchara. With 638 total appearances to his credit, he also scored a league-best 11 goals from free kicks. Viera was one of…

Viera made his debut for Uruguay on 18 July 2004 in a Copa América quarter-final match against Paraguay, having been called as a late replacement for injured starter Fabián Carini. He also featured in the penalty shootout loss to eventual winners Brazil. In five years, Viera earned 15 caps.

Viera started working as a coach in the country where he had retired, being appointed at Primera B team Real Cartagena on 20 August 2024. Under his tenure, they reached the semi-finals of the tournament, missing out on a chance to play a promotion play-off by placing third in the season's aggregate table; he left by mutual agreement on 21 April 2025, following a 3–2 loss at home to Jaguares de Córdoba. On 1 September 2026, Viera signed as head coach of his former club Junior.

Viera's father, also named Mario, was also a professional footballer and a goalkeeper.