AC Milan came away from the first-leg of their Champions League qualifier to PSV Eindhoven a 1-1 draw, while Lyon and Celtic both suffered defeats.
Milan striker Stephan El Shaarawy opened the scoring in the 15th minute, nodding in from Ignazio Abate's cross.
PSV equalised around the hour mark when Milan goalkeeper Christian Abbiati let a shot from Jeffrey Bruma spin up off him and Tim Matavz headed the ball into the net.
Lyon look to have a tough task on their hands to make it through to the group stage after their first leg against Real Sociedad ended in a 2-0 home defeat.
Frenchman Antoine Griezmann put the visitors in front in the 17th minute with an acrobatic effort and the advantage was doubled in the 50th minute when Haris Seferovic's volley caught out goalkeeper Anthony Lopes.
Things got even worse for Lyon in the 75th minute as Milan Bisevac was sent off having picked up a second yellow card.
Zenit St Petersburg's progression seems all but secure already at the half-way point of their tie against Pacos Ferreira after they claimed a 4-1 aggregate lead from the first leg in Portugal.
Roman Shirokov netted a hat-trick, with his second goal coming two minutes after Andre Leao's volleyed equaliser.
Zenit's third came through an own-goal by goalkeeper Matias Degra and Shirokov wrapped up his treble in the final moments.
Viktoria Plzen have the advantage in their tie against Maribor, winning the first leg 3-1 at home.
They were 1-0 up early on through Marian Cisovsky and added another goal via Vladimir Darida 13 minutes into the second half, shortly before Ales Mejac pulled back a goal for the away side with a delightful strike.
Michal Duris restored the two-goal cushion with a minute of normal time to go.
Celtic have left themselves with it all to do to reach the Champions League after a surprise 2-0 defeat to Kazakhstan champions Shakhter Karagandy in the first leg of their play-off at the Astana Arena.
Information from the Press Association was used in this report.