The German club will face the Catalan giants in a glamour friendly to celebrate their 125th anniversary, but insist that their Argentine superstar must featureFor all the latest reports and transfer rumours, visit our dedicated section here.
Hamburg will withhold up to €1.2 million (£936,000) in appearance fees from Barcelona if Lionel Messi does not play when the two sides meet in a pre-season friendly on Tuesday, Bild reports.
The illustrious friendly against the former Champions League winners has been arranged to coincide with the 125th anniversary of the German club, who are themselves former winners of the European Cup.
The report states that the Imtech Arena has been completely sold out for the visit of the Blaugrana, as Hamburg prepares to celebrate a milestone in the club's history.
However, it is believed that a clause was written into the contract for the friendly that stipulates that Messi must feature in the game.
The same clause does not apply to team-mates Andres Iniesta and Xavi, both of whom are just returning to pre-season training following Spain's successful European Championship campaign.
"It must be assumed that he plays," die Rothosen CEO Joachim Hilke was quoted as saying by Bild, with the potential appearance of the Argentine international expected to be the main draw.
The friendly on Tuesday kicks off at 18:00CET.