Real Madrid will get their first indication on Tuesday of whether unprecedented spending on players of more than $800 million over the past five years can secure the 10th European crown they have been chasing since 2002.
World-record signing Gareth Bale, who alone cost $133 million when he joined from Tottenham Hotspur this month, is likely to line up with Cristiano Ronaldo when Real begin their Champions League campaign at Group B rivals Galatasaray.
Wales winger Bale scored on debut in Saturday's 2-2 Primera Division draw at Villarreal, while Portugal forward Ronaldo netted his 203rd goal in as many official matches for the Spanish giants.
Real, the world's richest club by income, have splurged $817m on players in the last five years, according to the latest Prime Time Sport Football Transfer Review.
Their outlay is almost three times as much as European and Bundesliga champions Bayern Munich, who have spent $303m, and only English Premier League side Manchester City come close with an outlay of $733.
Real were boosted by the news on Sunday that Ronaldo had agreed a contract extension until the end of the 2017-18 season and club president Florentino Perez said the deal was in line with the club's long-term policy of fielding the world's best players.
"(Former president) Santiago Bernabeu showed us that this team should always count on the best," the construction magnate told reporters.
"This is one of the main facets of our identity and with Cristiano we have the best," he added.
"Those of us lucky enough to have seen Alfredo Di Stefano play always say that in Cristiano we have the continuation of such unique giants of the game capable of making history."
Real, whose draw at Villarreal was their first setback in four Primera Division matches this term, travel to Istanbul with a question mark over coach Carlo Ancelotti's policy of rotating goalkeepers Iker Casillas and Diego Lopez.
Spain captain Casillas lost his place in the starting line-up last season after falling out with Ancelotti's predecessor Jose Mourinho and the Italian has decided that Lopez will play in the Primera Division and Casillas in the Champions League.
The situation has prompted speculation that Casillas, a fixture for club and country for more than a decade and a hero to Real fans, could leave in the next transfer window in January.
"The decision is taken," Ancelotti said after the Villarreal game.
"Iker and Diego know it and there is no problem."
Galatasaray's disappointing start to the domestic season continued on Friday when they drew 1-1 at home to Antalyaspor, a third successive stalemate.
Speaking after the game, coach Fatih Terim was critical of the team's failure to put away their chances but confident about the upcoming match.
"We don't like losing points but the Real Madrid match will be different," said Terim, a former Turkey and AC Milan coach.
"On our own pitch and in front of our own fans I think we will benefit from the famous Ali Sami Yen Arena pressure."
Galatasaray's hopes will rest on the attacking duo of former Chelsea striker Didier Drogba, who scored the equaliser in Friday's match, and Burak Yilmaz, the top scorer in the domestic league for the last two seasons.
The club have been boosted by the arrival from Sporting Lisbon of Portuguese winger Bruma, one of the most promising youngsters in the nation's under-20 side.
Defender Semih Kaya needed treatment for a thigh problem after Friday's match, while Drogba and Brazilian midfielder Felipe Melo were in light training over the weekend after sustaining minor injuries.