Tottenham posted an opening 3-0 victory over LASK of Austria in its Europa League campaign on Thursday but Celtic suffered another setback with a home 3-1 loss at the hands of Zlatan Ibrahimovic’s AC Milan.
There were also wins for Spurs’ Premier League rivals Arsenal and Leicester.
Despite Gareth Bale starting for the first time since his return from Real Madrid, it was on-loan Carlos Vinicius who made an impressive debut as Tottenham enjoyed a 3-0 win in their Group J opener.
Vinicius started in place of the resting Harry Kane and he made goals in either half for Lucas Moura and Son Heung-min, while he would have also netted himself had Andres Andrade not scored an own goal.
Leicester made the perfect start in Group G with a comfortable 3-0 win over Zorya Luhansk of Ukraine.
James Maddison, Harvey Barnes and Kelechi Iheanacho were on the scoresheet.
In Glasgow, Celtic struggled against Serie A leader AC Milan, which was 2-0 up at half-time thanks to goals from Rade Krunic and Brahim Diaz.
Mohamed Elyounoussi reduced the arrears after the break, but Jens Petter Hauge broke clear to secure Milan’s Group H win in stoppage time.
Earlier, Arsenal came from behind to down Rapid Vienna 2-1. After a goalless first half it went behind when keeper Bernd Leno fluffed a clearance on a night he will want to forget.
But the Gunners then turned the game around in four second half minutes.
Important results: Group A: Young Boys 1 (Nsame 14-pen) lost to Roma 2 (Peres 69, Kumbulla 74).
Group B: Rapid Vienna 1 (Fountas 51) lost to Arsenal 2 (Luiz 70, Aubameyang 74).
Group C: Bayer Leverkusen 6 (Amiri 11, Alario 16, Diaby 61, Bellarabi 79, 83, Wirtz 87) bt Nice 2 (Gouiri 31, Claude-Maurice 90).
Group F: Napoli 0 lost to AZ Alkmaar 1 (De Wit 57).
Group G: Leicester City 3 (Maddison 29, Barnes 45, Iheanacho 67) bt Zorya Luhansk 0.
Group H: Celtic 1 (Elyounoussi 76) lost to AC Milan 3 (Krunic 14, Diaz 42, Hauge 90+2).
Group J: Tottenham 3 (Lucas 18, Andres Andrade 27-og, Son Heung-min 84) bt LASK 0.