Pep Guardiola knows "it does not take a genius" to know Manchester City must improve if they are to knock Real Madrid out of the Champions League.
City began this week with a significant victory off the field as the Court of Arbitration for Sport overturned their two-year ban from UEFA competitions, finding allegations of Financial Fair Play violations to be either "not established" or "time-barred" under regulations set out by European football's governing body.
On the field, it has been a different story, with Guardiola critical of his players' performance in Saturday's 2-0 FA Cup semi-final defeat to Arsenal.
Despite winning the EFL Cup in March, City's meek Premier League title defence in 2019-20 means their campaign will ultimately be judged on how the reformatted Champions League plays out.
They hold a 2-1 advantage over Madrid before the second leg of the last-16 tie at the Etihad Stadium on August 7.
The winner will progress to an eight-team straight knockout tournament in Lisbon the following week, taking on whoever prevails from the match-up between Juventus and Lyon – the Ligue 1 side 1-0 to the good at halfway.
Madrid have won 10 out of 10 since returning from lockdown to wrap up La Liga glory, while losses to Chelsea and Southampton have taken City's overall tally of Premier League defeats to nine this term.
"I don’t have to tell them. They know it, they feel it," said Guardiola, who also felt his players deserved to lose their 2-1 midweek win over relegation-threatened Bournemouth.
"We know the standards that we have to be on these kinds of stages, in these kind of competitions. Maybe we are learning, maybe not. We will see.
"The last game against Bournemouth was not good and today the first half was not good. We struggled to play at our level.
"It does not take a genius to realise we have to increase our standard against Madrid if we want to have any chance to go through."
Raheem Sterling, Kevin De Bruyne and Riyad Mahrez all went close to a second-half equaliser before Pierre-Emerick Aubameyang completed his brace in the 71st minute.
Mahrez's effort, sharply stopped by Arsenal goalkeeper Emiliano Martinez at his near post, was City's only attempt on target, but Guardiola felt the game was lost during a lacklustre first period.
"We didn't make a good performance," he said, after City failed to prevail in a domestic cup tie for the first time since February 2018.
"We can lose the game. My regret is we didn't play the first half like we played the second one.
"Sometimes it happens. It's an incredible run but sometimes you can lose. But the way we lost, particularly in the first half, we're sad about this."