The midfielder has left the West Midlands club six years after joining from French giants Paris Saint-Germain.
"I don't know where I'm going but I hope to stay in the UK," the 28-year old said.
"I wish West Bromwich Albion all the best. "I hope to play against them next season, in 'my house', against 'my fans'. This club is more special to me than Paris.
"PSG was the academy for me, where I became a professional. But this club gave me everything, they gave me the opportunity to play at the highest level.
"People know me now because I played for West Bromwich. I thank them for that."