MANCHESTER - A Champions League winner's medal is the only accolade missing from Sergio Aguero's list of honours as a Manchester City legend.
But his potential successor at the Etihad next season, Erling Braut Haaland, will pose the biggest threat if Pep Guardiola's men are to stumble at the quarter-final stage once more against Borussia Dortmund.
City have failed to get beyond the last eight in Guardiola's previous four seasons since taking charge in Manchester, but have won 26 of their last 27 games in all competitions to keep hopes of a historic quadruple alive.
Aguero is by a distance the club's all-time leading scorer with 257 goals, including the most important in City's history to snatch the Premier League title from Manchester United in 2011/2012.
His goals fired City to three more league titles, with his fifth a formality in the coming weeks.
Guardiola labelled Aguero's contribution "irreplaceable", not just in terms of goals and trophies won, but in the hearts and minds of supporters, who lived in United's shadow for so long prior to his arrival.
However, in his 10th and final season, the 32-year-old has been reduced to a peripheral figure.
Aguero has scored just three times in an injury and coronavirus-disrupted season.
- 'I know what we want' -
By contrast, Haaland's record of 49 goals in 50 games for Dortmund has shot him to the top of City's wish list to replace Aguero.
The Norwegian's record in the Champions League is even more impressive, becoming the fastest player ever to 20 goals in just 14 appearances in Europe's premier club competition.
Signed for just 20 million euros ($24 million) in January 2020, Dortmund are reportedly asking for 180 million euros for their prized asset this summer, with Europe's biggest clubs lining up to do battle for Haaland's signature.
His father, Alf-Inge Haaland, himself a former City player, and agent Mino Raiola reportedly travelled to Spain to speak with Barcelona and Real Madrid representatives last Thursday.
Guardiola claimed City may not be able to afford a replacement for Aguero due to the economic impact of the coronavirus pandemic.
But backed by Abu Dhabi state wealth, the reality is City have far greater resources to spend this summer than the heavily indebted Spanish giants.
"I am very, very relaxed about this matter because I know what we want," said Dortmund's sporting director Michael Zorc.
Yet, the German giants may find their hand forced by another economic blow.
Despite Haaland's prolific form, Saturday's 2-1 defeat by Eintracht Frankfurt left Dortmund seven points adrift of the Bundesliga top four with seven games to play.
"If you are realistic, even with six or seven wins it will be difficult to finish fourth," admitted defender Mats Hummels.
A return to the riches and prestige of the Champions League next season by winning this year's competition looks even more unlikely.
Even if Dortmund can shock City, a daunting semi-final against Bayern Munich or Paris Saint-Germain awaits.
Holding onto Haaland to play in the Europa League next season may prove as difficult a task for Zorc as defences have found stopping him from finding the net.