London - Pep Guardiola faces a major test of his managerial acumen after Manchester City's draining quadruple chase was dented by his decision to stray from his purist principles in their tired Champions League defeat at Tottenham.
One glance at City's starting line-up for Tuesday's 1-0 quarter-final first leg loss laid bare the concerns racing through Guardiola's mind before the latest obstacle in his team's gruelling bid to win all four major trophies.
Aware that his fatigued City stars had been feeling the physical and mental strain of competing on so many fronts, Guardiola was stirred into action by the lethargic nature of their 1-0 FA Cup semi-final win over Brighton on Saturday.
Watching City labour to kill off lowly Brighton at Wembley convinced Guardiola that taking on fired-up Tottenham, inspired by the buzz around their new stadium, with his traditional attacking gameplan would be risky.
So the City boss opted for an unusually conservative team that featured two defensive midfielders in Fernandinho and Ilkay Gundogan, while Riyad Mahrez was preferred to the more explosive but temperamental Leroy Sane on the right wing.
Playing the first leg away made some level of caution understandable, but rather than help City win the tactical battle, Guardiola's instruction to proceed with caution only served to lull his side into a submissive display that allowed them to be knocked out of any rhythm by Tottenham's relentless pressing.
There was a sense of deja vu about Guardiola's move as he played the same two defensive midfielders with disastrous consequences when City lost 3-0 at Liverpool in the Champions League quarter-final first leg last season.
The frenzied atmosphere at Anfield, which saw City's team bus attacked on the way to the stadium, clearly played a part in that loss.
But once again City's artists looked restricted by Guardiola's paint-by-numbers scheme.
"Guardiola seemed to put the handbrake on a little with the starting line-up he selected and the system he deployed," former Arsenal defender Martin Keown told the Daily Mail.
"This was one of the first times we've seen Guardiola adopt a more defensive strategy for a big match, and I feel it was linked to that loss at Anfield."
Sergio Aguero's failure to convert his first-half penalty was a major momentum swing.
Yet this was not a one-off - it was the third successive game in which City looked to be struggling with the demands of such a hectic fixture list.
Tired wins over Cardiff and Brighton preserved a City unbeaten run dating back to January 29, but the unconvincing nature of those performances were hidden by the growing hype over the quadruple.
Guardiola's selection at the Tottenham Hotspur Stadium showed he was not fooled, but finding solutions to keep City in contention in the Champions League and the Premier League will not be easy.
Kevin De Bruyne's slow return to peak form and fitness after a series of injuries this term has cast a shadow over Guardiola's plans, meaning the Belgian midfielder was not ready to face Tottenham after playing against Brighton.
"I decided to play with two holding players in that position. Fernandinho and Gundogan are more solid. If I played Kevin (De Bruyne) with one of the others it would be tough," Guardiola said in defence of his tactics.
Adding to Guardiola's problems, Aguero's return from two matches out with a muscle injury was supposed to reinvigorate City, but instead City's all-time leading scorer looked rusty and only lasted 70 minutes before coming off.
It must have been concerning for Guardiola that when Tottenham lost Harry Kane to a second-half ankle injury, it was the hosts rather than City who seized the initiative in the tie thanks to Son Heung-min's 78th-minute winner.
And the sloppy nature of the defending for Son's goal will have angered the City boss.
"Sometimes you play a lot with the ball and they have players who kill you on the counter-attack with one or two touches," Guardiola said ruefully.
"It is a good challenge for us. We will see in the next game how we are going to change."