The 21-year-old has struggled to find playing time with the Friulani since joining the club from Genoa in January.
As a result Gazzetta dello Sport are reporting that Merkel could return to Germany, with several Bundesliga clubs interested in acquiring his services.
The report indicates that in recent days PAOK, who finished 2nd in the Superleague Greece last season, have intensified talks with the Zebrette in order to land the former AC Milan player.
Merkel only managed to make five appearances for the Friulani after his January move last season. His most appearances in a season came in 2011 when he made 14 appearances for Genoa before moving to Milan in January.
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