Sergio Álvarez Díaz (born 23 January 1992) is a Spanish professional footballer who plays as a central midfielder for Segunda División club Eibar.

A product of Sporting de Gijón's prolific youth academy, Mareo, the 17-year-old made it to the reserves during the 2009–10 season, with the side playing in the Segunda División B.

[4] Álvarez scored the first of his four career goals in the top flight on 8 May 2016, in the 1–1 draw at Getafe CF.

[5] His second came the following weekend, his 78th-minute long-range effort in the 2–0 home win over Villarreal CF keeping his team up in the last matchday.

[6][7] On 26 July 2018, after spending 14 years at the club, Álvarez left Sporting and signed a four-year contract with SD Eibar in the top tier.