A Chelsea side much changed from the one that won the 2015 final beat Maccabi Tel-Aviv, while Dynamo Kyiv were one of three debutants to make their mark.
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- Holders Chelsea begin their title defence with a 3-0 win against Maccabi Tel-Aviv
- Debutants Dynamo Kyiv, Lyon and Valencia start with victories
- Only two of the 16 matchday one fixtures ended in a draw
- Watch highlights from four of this week's games in our video hub
Roma 0-0 Barcelona (watch rerun)
Carles Aleña struck the upright for Barcelona during a first half in which the Spanish side dominated possession. Roma were more of a force after the break, coming closest to scoring when Edoardo Soleri hit a post from Lorenzo Vasco's corner.
Leverkusen 1-0 BATE Borisov
Benjamin Henrichs marked a fine personal performance with the only goal 18 minutes from time. Henrichs created the best chance of the first half for Andrejs Cigaņiks and rattled the bar early in the second before sealing the points as he pounced when Cigaņiks was similarly denied.
Olympiacos 1-0 Bayern München
A late spot kick from captain Manolis Saliakas earned the Greek team victory in an evenly-balanced game. After a cagey start, Kostas Megaritis struck the crossbar with a close-range header on 42 minutes. The sides began the second half more aggressively but it was the hosts that won the the points with Saliakas's well-slotted penalty on 82 minutes.
Dinamo Zagreb 0-2 Arsenal
A piece of individual brilliance from Chris Willock on the cusp of half-time unlocked a well-drilled Dinamo Zagreb defence. The England Under-17 player received possession just inside the Dinamo half and left three opponents trailing as he burst into the area and found the bottom corner. Willock was then fouled for the spot kick that Ben Sheaf converted midway through the second period.
Chelsea 3-0 Maccabi Tel-Aviv
The Londoners made a winning start to their title defence as two goals from Kasey Palmer set up a comfortable triumph. Tammy Abraham completed the scoring late on for a Chelsea outfit featuring only three survivors of their starting XI in April's 3-2 final victory over Shakhtar Donetsk.
Dynamo Kyiv 2-1 Porto
Jorge met Bruno Costa's delivery as Porto hit the ground running, scoring from their first set piece in the third minute, but Dynamo bounced back. Olexiy Schcebetun smacked the post before teeing up Rostyslav Taranukha to made it 1-1 before the interval. The Ukrainian club kept up the momentum and their pressure told on 80 minutes when substitute Yevhen Smirniy headed in from a corner.
Gent 0-3 Olympique Lyonnais (watch re-run)
Romain Del Castillo claimed a goal in each half in a dominant display by the visitors. The 19-year-old could have had a hat-trick as he and Christopher Martins both blazed against the upright moments after the restart. Substitute Florian Ankoué slid in a third 18 minutes from time.
Valencia 2-0 Zenit
Valencia, like Lyon and Dynamo Kyiv, got their debut UEFA Youth League campaign off to a successful start. Rafael Mir Vicente made the points safe a quarter of an hour from time, adding to Carlos Soler Barragan's 29th-minute opener.