Despite all their domestic success in recent years, Man City have never gone beyond the semi-finals of the Champions League and Guardiola has found the competition equally vexing for much of the last decade
Pep Guardiola starts his latest bid to lead Manchester City to Champions League glory with the shadows of past failures casting doubt on his ability to secure that elusive title.
City host Porto in their opening Champions League group match on Wednesday with Guardiola's failing in the tournament weighing heavily on both the Spanish boss and his club.
Despite all their domestic success in recent years, City have never gone beyond the semi-finals of the Champions League and Guardiola has found the competition equally vexing for much of the last decade.
Since he won the Champions League as Barcelona boss for the second time in 2011, Guardiola has failed to return to the final of Europe's elite club competition.
That nine-year drought includes four years of frustration since he took charge at City in 2016.
In that time, Guardiola has seen City beaten by Monaco in the last 16 and Liverpool, Tottenham and Lyon in the quarter-finals.
He also lost in three semi-finals during his time as Bayern Munich manager before moving to City.
Last season's shock 3-1 defeat against Lyon in Lisbon was especially galling as City were heavy favourites against the French side.
Guardiola deserved a large portion of the blame for that letdown after his tactical tinkering appeared to unsettle his players and did nothing to tilt the tie in City's favour.
Interpreted by Guardiola's critics as further proof that his Champions League success at Barcelona was due to the presence of the great Lionel Messi's presence, the only bright side of the Lyon loss was that it was not their farewell to Europe for a while.
- Long-term plans -
For several months last season, it appeared City would not even be competing in the Champions League this term after UEFA gave them a two-year ban from European competitions for Financial Fairplay breaches.
City's legal dream team won that battle and the suspension was eventually thrown out on appeal.
Whether Guardiola can be as successful in Europe as City's Abu Dhabi-based owners were in the court room remains far from certain.
Adding to the unease around City ahead of their European campaign is the unresolved issue of Guardiola's future.
Guardiola is out of contract at the end of the season and has yet to agree a new deal amid speculation that he may decide to leave the Etihad Stadium in 2021.
For now, Guardiola will focus on Porto's visit to Manchester rather than entertaining questions about his long-term plans.
The 49-year-old insists he has to earn a prolonged stay at City by improving on last season's disappointment, which saw them surrender the Premier League to Liverpool and win only the League Cup.
There have been some worrying signs already as Leicester thrashed City 5-2, while Saturday's 1-0 win against Arsenal was far from convincing.
Significantly, Guardiola was able to welcome back Sergio Aguero last weekend as City's record goalscorer made his first appearance for four months after knee surgery.
City have lacked a cutting edge in Aguero's absence and Guardiola's hopes of a serious Champions League challenge hinge on the Argentine striker staying fit.
"The important thing is that Sergio comes back in good physical condition, starts to get his rhythm, doesn't get more injuries and plays good," Guardiola said.
"We know what he means for us, we know how we appreciate him, but now he has to show like every one of us, me first, that we deserve to continue here and playing good and winning games."