Guardiola insists even an FA Cup win would not salvage a season that has been mediocre by the standards of a side that reeled off a historic four successive Premier League titles.
There was, however, no disguising the City manager's burning desire to add another trophy to his haul and avoid the rare ignominy of ending a campaign without silverware.
He picked a strong side and his animated, often frantic, body language from the first whistle showed how much he wanted another trip to Wembley for the semi-final.
Guardiola's experienced line-up was full of serial winners - and he acted decisively when they reached half-time in arrears against this energetic, skilful Bournemouth side.
He removed the struggling Khusanov to send on O'Reilly, putting him at left-back and switching Josko Gvardiol into the centre.
Guardiola's switch gave City the cutting edge they had lacked as O'Reilly first set up Haaland with an inviting delivery then provided an assist for match-winner Marmoush as the visitors dominated the second half against the fading Cherries.
The only cloud for City was the injury to Haaland that forced him off after an hour, with the striker appearing to twist his left ankle in a touchline tangle with Lewis Cook.
This was a display that highlighted City's flaws and strengths, but the habit of winning trophies is one that will die hard for Guardiola and his players.