The 19-year-old, who became Israel's youngest international when he made his debut at the age of 17 in 2007, has penned a four-year contract with the Primera Division team.

Sahar joined Chelsea from Hapoel Tel-Aviv in 2006 and spent the latter part of last season on a six-month loan at Eredivisie club De Graafschap.

The player has also spent time on loan at Queens Park Rangers, Sheffield Wednesday and Portsmouth.

He was eligible to play in the Premier League immediately because he acquired Polish citizenship due to his mother's Polish origin.

Sahar has scored three goals for the Israel national team.