Dortmund boss Peter Stöger admitted being disappointed with his side's performance after they were beaten 2-1 Red Bull Salzburg at the Westfalenstadion in the Europa League's round of 16 on Thursday.
The Austrian champions stunned their opponents early in the second half when Valon Berisha struck twice in the space of seven minutes. Andre Schurrle tapped in Christian Pulisic's cross in the 62nd minute to reduce the deficit, but the visitors held on as the Bundesliga side slumped to their first defeat in 2018.
Speaking after the game, boss Stoger, who took over at Dortmund in December following the sacking of Peter Bosz, conceded his side deserved to lose and will need to improve for the reverse fixture.