Australia's contingent in the Europa League had a tough night with James Holland injured early in LASK's defeat at Tottenham while Tom Rogic was a substitute for Celtic in their home loss to AC Milan.
Holland, an ever-present in the hears of Austrian side LASK's midfield, was replaced after just five minutes at Tottenham Stadium with what appeared to be a right lower leg problem as Spurs secured a 3-0 Group J win.
Gareth Bale made the first start of his second spell with Tottenham, who breezed to victory with goals from Lucas Moura (18th) and substitute Son Heung-Min (84th) either side of an own goal from Andres Andrade.
Socceroos attacking midfielder Rogic came off the bench in the 64th minute with the Hoops two goals down before Milan closed out a 3-1 victory in Group H.
Rade Krunic (14th), Brahim Diaz (42nd) and Jens Hauge (90th) were all on the scoresheet as AC Milan prevailed 3-1 at Celtic, who scored a consolation through substitute Mohamed Elyounoussi.
Australian defender Milos Degenek also suffered defeat on matchday one with his Serbian outfit Crvena Zvezda suffering a 2-0 loss away to Hoffenheim.
Degenek started the match in defence but was unable to slow down his German opponents with second-half goals from Christoph Baumgartner and Mu'nas Dabbur enough to guide the Bundesliga side to victory.
Napoli started their Group F campaign with a shock 1-0 defeat at home to AZ Alkmaar while Arsenal's blushes were spared by second-half goals from David Luiz and substitute Pierre-Emerick Aubameyang in their 2-1 come-from-behind Group B win at Rapid Vienna.
Alkmaar had travelled to Italy with 13 of their players sidelined because of coronavirus, but the Dutch runners-up prevailed courtesy of Dani De Wit's 57th-minute goal.
A mistake by Arsenal goalkeeper Bernd Leno gifted a goal to Taxiarchis Fountas as Rapid Vienna to a 51st-minute lead but the Gunners hit back to win 2-1 at at the Allianz Stadion, where 3,000 home fans watched on.
James Maddison, Harvey Barnes and Kelechi Iheanacho were all on target as Leicester showed no signs of missing the injured Jamie Vardy in a 3-0 win over Zorya Luhansk in Group G, where Braga brushed aside AEK Athens by the same scoreline.
Roma came from a goal down to claim a 2-1 victory at Young Boys while also in Group A CFR Cluj ran out 2-0 winners at CSKA Sofia.
James Tavernier's 19th-minute penalty and substitute Kemar Roofe's halfway line goal in time added-on lifted Rangers to a 2-0 win at a rain-lashed Standard Liege in Group D while Uruguayan striker Darwin Nunez's hat-trick propelled Benfica to a 4-2 victory at Lech Poznan.
Paco Alcacer's brace helped Villarreal defeat Sivasspor 5-3 in Group I while Maccabi Tel-Aviv beat Qarabag 1-0.
Bayer Leverkusen hammered Nice 6-2 in Group C as Hapoel Be'er Sheva overcame Slavia Prague 3-1.
Granada defeated PSV Eindhoven 2-1 in Group E while PAOK Salonika drew 1-1 with Omonia Nicosia.
In Group K there were draws between Dinamo Zagreb and Feyenoord, 0-0, and Wolfsberg and CSKA Moscow, 1-1.
In Group L, Hoffenheim beat Red Star Belgrade 2-0 and Slovan Liberec accounted for Gent 1-0.
Elsewhere, Lille romped to a 4-1 victory over 10-man Sparta Prague, Real Sociedad won 1-0 at Croatian club Rijeka, Norwegian champions Molde won 2-1 over Irish side Dundalk and Royal Antwerp beat Ludogorets 2-1.