West Ham suffered more jitters against Astra Giurgiu as they were held to a 1-1 draw in the first leg of their Europa League playoff on Thursday.
The Hammers, bidding to reach the group stages for the first time, looked set to take a 1-0 lead back to the London Stadium next week thanks to Mark Noble's penalty on the stroke of half-time.
However, Romanian champions Astra, who beat Slaven Bilic's side in last season's qualifiers, stunned the visitors again when sub Denis Alibec hit a late equaliser.
In the 83rd minute, West Ham failed to clear a near-post corner and Alibec swivelled to rifle a fierce drive across Darren Randolph and into the top corner.
Serie A side Sassuolo put one foot in the group stage with a 3-0 win at home against Red Star Belgrade.
Domenico Berardi opened the scoring in the 17th minute before Matteo Politano added a second before the break, and Gregoire Defrel put Sassuolo firmly in control in with a volley in the second half.
Seba scored in the first half to give Olympiakos a 1-0 win at Portuguese side Arouca, while their Greek rivals Panathinaikos enjoyed a 3-0 win at home over Brondby.
Brondby's Svenn Crone was sent off for a second booking after just 33 minutes, and Marcus Berg gave Panathinaikos the lead in first-half stoppage time.
It got worse for the Danish club as Frederik Ronnow was sent off early in the second half and Cristian Daniel Ledesma coverted a penalty before Berg found the net again.
Shakhtar Donetsk earned a 2-1 win in Turkey at Buyuksehir thanks to a Sokol Cikalleshi own goal before Viktor Kovalenko added a second goal ahead of half-time. Emre Belozoglu's penalty had earlier given the hosts hope.
Miroslav Stoch scored two late goals to help Fenerbahce open a 3-0 advantage over Grasshoppers, after Aatif Chahechouhe's opener.
Patrick Banggaard's own goal was enough to gift Osmanlispor a 1-0 win at Midtylland.
Belarusian side BATE Borisov have reached the Champions League five times since 2008 but are on the brink of failing to qualify for either European competition proper this term.
Astana eased past BATE 2-0 to take the early advantage in their play-off tie, with Junior Kabananga and Azat Nurgaliyev on target.
Stijn Wuytens' brace and a strike from Fred Friday helped AZ Alkmaar secure a 3-0 win at Vojvodina.
Anderlecht eased to a 3-0 triumph at Slavia Prague thanks to goals from Idrissa Sylla, Lukasz Teodorczyk and Sofiane Hanni.
Kalifa Coulibaly and Thomas Matton registered as Gent saw off Shkendija 2-1 at home, with Besart Ibraimi on the scoresheet for the away side.
Leon Bailey's penalty and a Mbwana Samatta goal helped Genk grab a 2-2 draw at Lokomotiv Zagreb, Mirko Maric converting a spot-kick and Ivan Fiolic also on target for the hosts.
Dinamo Tbilisi bombed out 3-0 at home to PAOK, with Leo Matos, Jose Angel Crespo and Facundo Pereyra supplying the goals for the travelling Greeks.
Liberec claimed a 1-0 win at AEK Larnaca, Vladimir Coufal on target and Juanma Ortiz sent off for the hosts.
Gal Alberman and Ezequiel Scarione ensured Maccabi Tel Aviv edged out Hajduk Split 2-1 in Israel, with Ahmed Said notching for the visitors.
Alexander Grunwald and Felipe Pires handed Austria Vienna a 2-1 home victory over Rosenborg, while Louis Schaub bagged a hat trick as Rapid Vienna thumped Trencin 4-0, with Stefan Schwab also on target.
Bagaliy Dabo's two-goal brace in three minutes sealed Qabala's 3-1 home win over Maribor, with Sergei Zenjov adding the third goal. Tavares had earlier put Maribor into a 1-0 half-time lead.
Mads Albaek's goal handed Gothenburg a 1-0 home win over Qarabag,
Sonderjyske held Sparta Prague to a goalless draw, while Krasnodar thumped Partizani 4-0. Joaozinho blasted home a penalty, with Artur Jedrzejczyk and Fedor Smolov also scoring and Gezim Krasniqi registering an own goal.