Nigerian youngster Kelechi Iheanacho was conspicuously absent as Manchester City for the first time failed to win a competitive game under coach Pep Guardiola.
The Citizens had won all their previous 10 matches before Wednesday’s game away at Glasgow where they could only force Celtic FC to a 3-3 draw.
The dropped points notwithstanding, City showed great character as they came back from behind thrice to draw the game, with Celtic looking very inspired in front of their home fans.
Elsewhere, another Nigerian, Alex Iwobi was in the thick of action with Arsenal as the Gunners beat Basel 2-0 at the Emirates.
Iwobi bagged 70 minutes of impressive display as Theo Walcott secured Arsenal a comfortable win over the Swiss Champions.
At the Borussia Park, Barcelona secured their second successive win on the continent after coming from behind to beat Bundesliga side Borusssia Mochengladbach 2-1.
Also, Paris Saint German picked their first win in the UEFA Champions League with a 3-1 demolition of Ludogorets Razgrad courtesy a brace from Edinson Cavani and a goal from Blaise Matuidi.
Atletico Madrid Wednesday night ended Carlo Ancelotti and Bayern Munich’s perfect start to the season as they repeated their 1-0 win from last season’s Champions League semi-finals in the Match Day 2 contest.