Champions League finalists Borussia Dortmund face a nervous after new signing Henrikh Mkhitaryan suffered an ankle injury in a pre-season friendly and will undergo a scan on Wednesday.
The 24-year-old, who cost Dortmund 27.5 million euros ($36 million) from Shakhtar Donetsk, scored in Dortmund's 4-1 win over FC Luzern on Tuesday but limped off and Borussia face an anxious wait just over three weeks before the new Bundesliga season starts.
"He went over on the ankle, which is strapped, and now we have to wait and see," said Dortmund coach Jurgen Klopp, whose side host Champions Leaguer winners Bayern Munich in the German Super Cup on July 27.
Dortmund are in the midst of their pre-season training and play in a four-team tournament this weekend which includes Hamburg, hosts Borussia Moenchengladbach and European Cup-winners Bayern.
Meanwhile, Dortmund's want-away striker Robert Lewandowski has admitted he faces another season at Borussia with his contract due to expire in June 2014.
The 24-year-old has made no secret of his desire to move to a bigger club, with strong rumours he will join Bayern, but Dortmund have received no offers for the Poland hot-shot.
"I have to accept that I must stay in Dortmund," Lewandowski told German daily Bild.
"I played and scored in the knowledge that I was allowed to leave in the summer."
Lewandowski, who scored four goals in the Champions League semi-final, first leg win over Real Madrid in April, said talks with Dortmund had led him to believe he could change clubs.
His agent and manager were quoted on numerous occasions saying a move to a big club was imminent at the end of the season but Borussia received no offers for the striker and will hold the Poland star to his contract.
Bayern chairman Karl-Heinz Rummenigge last week said of Lewandowski: "I am quite optimistic that the player will move to Bayern next summer."
But Dortmund coach Jurgen Klopp has said Lewandowski is working hard in training.
"He couldn't be more professional," said Klopp after Lewandowski scored in last week's friendly win against Turkish side Bursaspor and then on Tuesday at FC Luzern.