AC Milan continued their fine run of form as the Serie A leaders eased to their way to a 3-1 victory over Celtic last night in Glasgow.
It was all too easy in the first half for the Italians as goals from Rade Krunic and Brahim Diaz gave the visitors a two-goal lead.
However, Mohamed Elyounoussi sparked hope when he reduced the deficit, but Jens Petter Hauge broke clear to secure Milan's win in stoppage time.
The Hoops will have a lot of work to do if they are to qualify from this group after this home defeat.
Meanwhile, Pierre-Emerick Aubameyang came off the bench to spare the blushes of goalkeeper Bernd Leno as Arsenal scored twice in four minutes to earn a Europa League victory over Rapid Vienna.
After a mistake by Leno gifted a goal to Taxiarchis Fountas, the Gunners had to rally with David Luiz and Aubameyang on target as Arsenal claimed a 2-1 win at the Allianz Stadion, where 3,000 home fans watched on.
Gareth Bale started for Tottenham Hotspur for the first time in seven years and helped them to a 3-0 win over Austria's LASK. Lucas Moura opened the scoring after 18 minutes and Bale's square pass was turned into his own net by Andres Andrade nine minutes later for a two-goal half-time lead.
Substitute Son Heung-min added the third in the 84th minute to ensure a winning start for Spurs to their Group J campaign.
Elsewhere, Leicester made the perfect start to their Europa League campaign after a comfortable 3-0 win over Zorya Luhansk. James Maddison, Harvey Barnes and Kelechi Iheanacho were on target.