Tottenham Hotspur fell 1-0 at Gent and Borussia Moenchengladbach lost with the same result at home against Fiorentina in the Europa League soccer competition on Thursday (Friday AEDT).
Spurs dominated the last-32 contest in Belgium but were beaten by Jeremy Perbet's winner, meaning they will have to stage a comeback effort in a week's time at Wembley.
Gladbach must even reverse matters in Italy on February 23 after being wasteful and defeated by a stunning free-kick from Federico Bernadeschi.
Russia's Rostov meanwhile took a big step towards the last 16 with a 4-0 drubbing of 10-man Sparta Prague, and so did Olympique Lyon who triumphed 4-1 at Dutch side AZ Alkmaar.
Tottenham were in control at Gent with Dele Alli firing wide from long range in the 12th minute and Harry Kane denied by the right post in the 49th.
But they were beaten 10 minutes later when Danijel Milicevic found Perbet in the area and the midfielder struck into the bottom right corner on his second attempt after the first was blocked.
Spurs defender Eric Dier told BT sport that the goal 'stopped us in our tracks' but remained upbeat overall.
'I don't see why we cannot turn it around. We ... lacked a bit of quality. At home we will be better,' he said.