Aspiring to the coronation, Manchester City was scared at home in front of Dortmund.
His kid Phil Foden, started in place of Raheem Sterling, finally stole the limelight from Erling Haaland, 20 years old like him, with a saving goal scored in the 90th minute.
An infuriating outcome for the German club.
Guardiola's team, presented as ultra-favorite against Borussia, thought they had paved the way for easy success with an early goal from Kevin De Bruyne (19th), well helped by the valuable work of Riyad Mahrez.
Still, the visiting club found the resources to equalize in the 84th minute by captain Marco Reus.
Determined to win, the English nevertheless regained the advantage over the gong by Foden (90th).
Haaland decisive passer
For the Citizens, the plan was simple: it was to muzzle the Norwegian nugget Haaland, colossus with agile feet who remained on four consecutive doubles in the Champions League, a record.
Guardiola's tactical set-up has proven its worth but it has cracked once.
Haaland, C1 top scorer with ten pawns in seven games, this time turned into a decisive passer.
In the return match, the young blond colossus (1.93 m) can surely once again give Manchester City a cold sweat.
His father's former club, Alf Inge Haaland, had not conceded a single goal in their last seven European Cup games.
