Atletico Madrid showed why they are one of the favourites for the Champions League title, with the beating of Bayern Munich, while Pep Guardiola's winning run after taking over as Manchester City manager came to an end in Scotland. Arsenal were as comfortable as they come against Basel at the Emirates, with Barcelona needing a second half comeback to avoid defeat in Germany.
PSG were another team that needed to come from behind to avoid an upset loss to Ludogorets, with Italian side Napoli turning on the goalscoring style in their win over Benfica.
Atletico vs Bayern was always going to be a close encounter and so it proved to be with a Yannick Carrasco strike, which came about after the Spanish side won the ball in Bayern's own half, proving to be the clincher.
Bayern, despite the loss, however, remain in a strong position to go through from the group. They have three points from two matches, with Atletico leading with six. Rostov and PSV Eindhoven, after their 2-2 draw, have a point each in Group D.
Group A saw both the heavyweights pick up wins, but in contrasting fashion. Arsenal were in cruise control from minute one, playing that silky football everyone loves to see and making life difficult for FC Basel. David Ospina had a pretty serene outing in goal, with the Gunners beating the Swiss side courtesy Theo Walcott's first half double.
PSG were made to sweat a little more for their win, with Ludogorets taking the lead in the 16th minute after Natanael found the back of the net from a freekick. Blaise Matuidi equalised four minutes from the first half, before a brace from Edinson Cavani in the second half gave the French champions a 3-1 victory.
Group C saw Napoli take control after a comprehensive 4-2 win over Benfica. Marek Hamsik, Dries Mertens and Arkadiusz Milik were all on target for the Serie A team, with Goncalo Guedes and Eduardo Salvio grabbing a couple of late consolation goals, after Napoli had gone 4-0 up late in the second 45. In the other game, Besiktas and Dynamo Kyiv played a 1-1 draw, giving Napoli a four-point lead in Group C with just two games played.
For a while it looked like Group D might be blown wide open as Borussia Monchengladbach held on to a 1-0 lead after Thorgan Hazard had scored in the 34th minute. However, an Arda Turan equaliser five minutes past the hour and a Gerard Pique winner nine minutes later saved Barca's blushes, with the Spanish side doing just enough in the absence of the injured Lionel Messi.
Barcelona lead the group with a perfect six points from two matches, with Manchester City two behind after Guardiola's side were held to a 3-3 draw by Celtic. City had to come from behind three times in the match as they saw a 10-game winning run in all competitions to open the season brought to an end by Brendan Rodgers' determined side.
Champions League results: Group A: Ludogorets 1-3 PSG, Arsenal 2-0 Basel.
Group B: Besiktas 1-1 Dynamo Kyiv, Napoli 4-2 Benfica.
Group C: Borussia Monchengladbach 1-2 Barcelona, Celtic 3-3 Manchester City.
Group D: Atletico Madrid 1-0 Bayern Munich, Rostov 2-2 PSV Eindhoven.