Never had one of his teams lost before the semi-finals in the competition but that prospect suddenly seemed real.
Damned to succeed, Guardiola repeatedly said he was aware of what he needed to deliver at the five-time European champions for whom a league and German Cup double was just not enough.
He arrived at Bayern after their 2013 treble-winning season and expectations have not been lowered since. A semi-final exit last season only heightened pressure on Guardiola to deliver another treble this time round.
But plagued by injuries in recent months and a rare internal strife after long-time team doctor Hans-Wilhelm Mueller-Wohlfahrt quit after 38 years, saying his medical team was blamed for the loss to Porto, Bayern had a far-from-perfect preparation.
The doctor is hugely respected by Bayern players with many saying they would continue taking his advice and Guardiola suddenly in the firing line for allegedly falling out with a Bayern icon.
Failure to advance against Porto would have added to an already difficult week and would no doubt fan speculation about the coach’s future in Munich despite having a contract to 2016.
With Premier League clubs circling, a slip-up on Tuesday could prove decisive for both the club and the coach.
But the Spaniard, who won 14 titles in his four seasons at Barcelona, thrived under adverse conditions with his team playing arguably their best game this season, even without injured Arjen Robben, Franck Ribery, Bastian Schweinsteiger and David Alaba.
“I felt it in the last few days that we would advance,” Guardiola said after Bayern fired five goals in 26 first-half minutes.
“This is about life or death and I know how very important it was,” he said. “I know what is expected of me in this team. It is about winning just like at Barcelona.”
Fans are now dreaming of a trophy on German soil in June’s final in Berlin and with players gradually returning from injury, Guardiola is confident Bayern will further improve.
“We can play even better,” he said in what is no doubt a warning to other title contenders. “After the loss in Porto the players were my heroes. Now it’s easy to love them.”
(Editing by Amlan Chakraborty)