The Romania international had his contract cancelled by mutual consent before Monday's transfer deadline.
It means he is now free to join another club as a free agent.
"When I arrived at the club I thought West Brom could do big things because of the players," said Tamas.
"There was a good group, with everyone playing for their national team.
"There was and are good quality of players who play good football.
"I think West Brom can aim for the top six - and I'll be checking on their results.
"It's sad to say goodbye - but I need to move on."
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