Razvan Rat was signed by West Ham last summer on a free transfer, but after 15 appearances in the Premier League, the Hammers elected to release him in January.
The Romanian international signed with La Liga side Rayo Vallecano where he has featured eight times.
He is now however in big trouble with the league's disciplinary board, facing a four game ban after being sent off at the weekend.
The full-back was dismissed after a needless off the ball headbutt, which left opponent Charles, of Celta Vigo with a fractured nose.
Rat was given a straight red card and a ruling is expected to confirm the player's ban over the coming days.