Pep Guardiola says Manchester United's absence from Champions League is a 'lesson'

Bayern Munich manager Pep Guardiola weighed in on Manchester United's absence from the Champions League and used their plight as a warning to other clubs around Europe of the dangers of becoming complacent.

It's been almost 20 years since a Champions League campaign began without one of England's most successful clubs after United failed to qualify following a disastrous domestic campaign last season that saw them fall out of the top four in the Premier League.

Guardiola, whose team begins their journey in the Champions League when they play Manchester City on Wednesday, says United's fall should be viewed as a warning to all clubs about the importance of maintaining a desire to perform at the highest level on a weekly basis.

“It’s a good lesson for the big clubs,” said Guardiola, per The Telegraph. “They think ‘we are unbeatable and strong’ and they are not here and maybe the next season they are out.

“That’s why football is magnificent. Every single week you have to be ready. Every week you have got to show you are ready. A bad 45 minutes and you’re out.”

Manchester United spent £150 million ($243 million US) on new signings during the summer transfer window in an effort to improve on last year's seventh-place finish and return to the world's most lucrative tournament.