Borussia Dortmund coach Juergen Klopp said his players must improve after a narrow 2-1 win over Werder Bremen in their Bundesliga opener.
The hosts had coasted through much of the match after rocketing into an early lead through Marco Reus, but looked to have let two points slip when Theodor Gebre Selassie netted a 75th-minute equaliser.
Mario Gotze rose from the bench to bag a late winner, but Klopp said his troops showed they were unfit after 14 weeks without a league match.
