"There are indications that something is being planned for the start of the Bundesliga season," a spokesman for the interior ministry of Rhineland-Palatinate told AFP.
The 24-year-old man was arrested on Friday in Mutterstadt, a city in the western state, before investigators raided a flat in Duisburg, some 300 kilometres northwest in North Rhine-Westphalia state.
The interior ministry of North Rhine-Westphalia said there was "no concrete threat" but a witness had alerted the authorities to a planned Islamist attack.
The suspect, an asylum seeker from Syria, arrived in Germany at the start of the year and has been living in North Rhine-Westphalia, according to Germany's department for distributing refugees around the country, cited by the Südwestrundfunk channel.
Numerous photos of fighting in Syria were found on his phone and computer, the Südwestrundfunk report said, though it was not clear if he had taken them himself or downloaded them.
Duisburg prosecutors refused to comment.
League champions Bayern Munich will host Werder Bremen as the new season of Germany's first division football championships kick off on August 26th.
In July, the southern state of Bavaria suffered two attacks carried out by asylum seekers and claimed by Isis -- an axe rampage on a train in Wuerzburg and a suicide bombing in Ansbach.
In Würzburg the 17-year-old attacker was shot dead by police after injuring five people. In Ansbach 15 people were injured after a failed Syrian asylum seeker detonated his explosive outside a music festival, killing himself.
Raids in NRW and Lower Saxony
Police in North Rhine-Westphalia and Lower Saxony also conducted searches of properties associated with people in the Islamist scene on Wednesday as part of an investigation of Isis supporters in the Bundesrepublik.
The searches were conducted on orders from federal prosecutors.
The three accused have allegedly tried to recruit members for the terror group since January 2015. One of the men is also accused of financially and logistically supporting the jihadist organization.
No one was arrested during the searches.
Relevant police authorities confirmed the raids took place in Dortmund, Duisburg and Hildesheim.
According to eye witnesses police units were present in front of a tourism agency in Duisburg. Der Western reports that the manager of the agency is suspected of having had contact with two adolescents who carried out an attack on a Sikh temple in Essen earlier this year.