The 29-year-old man served prison time for an attempted similar robbery on the casino at the top of the Park Inn on Alexanderplatz in 2004, leading police to suspect him and his then gang to have been behind the latest heist.
But a day after his arrest the man was released without charge, leaving Berlin police back where they started.
The Tagesspiegel newspaper on Sunday reported that although officers had searched two Berlin flats connected with the man, they could not find anything to put him at the scene of the crime.
He was released on Saturday afternoon, the paper reported, after detectives realised on the basis of their questioning that he could not have been involved.
It seems he resembled security camera pictures of one of the gang who robbed the poker tournament last weekend. His previous involvement in a similar heist led the investigation team to his door.
No further details have been released in order to keep investigative information from those who were actually responsible for robbing €242,000 from the Grand Hyatt hotel on Potsdamer Platz last Sunday.
The four-member gang held up the international tournament, which had included a number of celebrities including Boris Becker, and ran of with bags of money.