Sunderland Association Football Club Current Players
Marcos joined Sunderland on a season-long loan from Serie A side Fiorentina in January 2014.
The Spaniard comes from good footballing stock with both his father and grandfather representing their country at international level.
His father, Marcos Alonso Imaz, spent eight years with Real Madrid, while grandfather Marcos Alonso Pena had spells with Atletico Madrid and Barcelona during his club career.
Marcos began his career as a youngster with Real Madrid and made a single senior appearance for the Spanish giants as well as spending time with the club's B side.
The left-back joined Bolton Wanderers in July 2010 and made 46 appearances during three seasons with the club - winning the Trotters' Player of the Year award in 2013.
He moved to Italy with Fiorentina last summer and made eight appearances for the Viola, with five of those coming in European competition.
Marcos will wear shirt number 28.
- 22El-Hadji Ba
- 4Ki Sung-Yueng
- 6 Cabral*
- 7Sebastian Larsson
- 8Craig Gardner
- 11Adam Johnson
- 14Jack Colback
- 15David Vaughan*
- 19David Moberg Karlsson*
- 23Emanuele Giaccherini
- 26Liam Bridcutt
- 33Lee Cattermole
- 35Charis Mavrias
- 41Duncan Watmore*
- Alfred N'Diaye*