Ferencvaros stunned Celtic 3-1 at Celtic Park on Thursday to hand Martin O’Neill another defeat and a disappointing start to the Europa League campaign.
The visitors took the lead in the 20th minute after Kieran Tierney failed to deal with a cross, allowing Bamidele Yusuf’s effort to take a deflection off Liam Scales before finding the net.
Celtic responded strongly and drew level shortly before half-time when Mika Baur converted Tierney’s cross in the 44th minute.
Their joy was short-lived, however, as Ferencvaros restored their advantage in stoppage time.
Yusuf beat Tierney and Callum McGregor before setting up Kristoffer Zachariassen, who flicked the ball beyond goalkeeper Viljami Sinisalo.
Ferencvaros extended their lead just two minutes into the second half when Celtic surrendered possession cheaply.
Daniel Arzani capitalised on the error, firing a superb strike into the top corner.
Celtic pushed forward in search of a way back into the game and created a number of late opportunities, but Ferencvaros held firm to secure all three points.
The result leaves O’Neill’s side with consecutive defeats after their League Cup loss to Rangers.
Celtic will have an immediate opportunity to respond when they face Rangers again in Sunday’s Scottish Premiership clash.
O’Neill admitted his team must quickly recover from the setback, saying, “It’s not the start we wanted. We have seven games in which to try and get some points on the board. Really need to concentrate now on Sunday [against Rangers].”
The Celtic manager also acknowledged that his side must improve their use of possession and eliminate the mistakes that have proved costly in recent matches.