Sergi was born in Nules, and started his career at his home town club before moving to Barcelona's academy in 2010. Here, he developed as both a winger or forward, and left La Masia in 2013. Aged 16, Sergi moved to Liverpool, where he progressed through the U18 team and eventually made his debut for Liverpool's reserves in August 2014. He then went on to appear in every match of Liverpool's 14/15 Youth League Campaign.

In 2015, Canos joined Brentford on loan, making his first senior appearance as a substitute in a 1-1 draw with Leeds United on 12 September 15. He would go on to make regular appearances, and scored his first senior goal against Nottingham Forest on 21 November. Sergi also scored Brentford's goal of the season, finishing with 7 goals from 39 appearances.

Returning to Liverpool in 2015, Sergi made one senior appearance before signing for Norwich City in 2016. During his time at Norwich, Sergi was mostly favoured in cup games, before returning to Brentford in 2017 on a four year contract.

Just five days after signing for Brentford, Sergi made his debut in a 3-3 draw with Brighton. He would score his first goals since his return to Griffin Park with a brace in a 5-3 win against Burton Albion. Sergi would finish the16/17 season with 18 appearances and 4 goals.

With reoccurring injury problems during the 17/18 season, Sergi was still able to end the season with 31 appearances and 3 goals.

Sergi featured mainly as a starter during the 18/19 season, and came into his own in late January, scoring four goals in four matches. Due to a lack of fit full backs, Thomas Frank began to deploy Sergi as a right wing back during February. Sergi finished the season with a career high 50 appearances and 9 goals.

Sergi began the 19/20 as a ever present starter on the wing, before he suffered a knee injury in October. Following this, he signed a new four year contract. He returned to training in February 2020 and began to make substitute appearances after the restart of football. Later, Sergi would credit the injury as an important moment in his career, as he had to improve his mentality and now understands how much it takes for top players to be playing in top leagues. The 19/20 season ended with Sergi making 15 appearances after defeat in the play off final.

Going from strength to strength in the 20/21 season, Sergi was primarily used on the left wing. His four goals and outstanding performances in December earned him nominations for Championship Player of the Month and PFA Fans' Championship Player of the Month awards. The season ended with promotion to the Premier League after a victory in the play off final. Sergi finished the 20/21 season with 55 appearances and 9 goals.

Starting Brentford's first Premier League season with a bang, Sergi scored in a 2-0 win over Arsenal, a goal which would later be voted the club's Goal of the Season. He showed his versatility throughout the season, and was deployed as a winger, right wing backy, and forward. After a short spell out with injury, Sergi returned to action on the final day of the season with a goal against Leeds United.

Sergi has represented Spain throughout his youth career, playing through until U19 level, when he appeared in Spain's qualifying campaign for the U19 European Championship.