Casemiro offered no excuses for Real Madrid's 3-0 loss to Paris Saint-Germain, admitting his team were below their best on Wednesday.
A brace from Angel Di Maria and a late Thomas Meunier goal saw PSG to their comfortable victory in the Group A clash at Parc des Princes.
While Madrid had two goals ruled out, they failed to record a single shot on target in a Champions League game for the first time since Opta started collecting the data in 2003-04.
Casemiro said there was still time for Madrid to recover, but the midfielder lamented a below-par performance.
"We have not played well, they [PSG] have had control of the game and we know that it is difficult to play here," he told Movistar .
"They are very strong, they have great players. There are no excuses, we have not played well, but there is still time for many things, to keep working.
"There are many things ahead."
Gareth Bale and Karim Benzema had efforts chalked off for Madrid, who were left bottom of a group that also includes Club Brugge and Galatasaray.
Casemiro felt Zinedine Zidane's side needed to produce close to a perfect display to have any chance, despite the Ligue 1 champions being without Neymar, Kylian Mbappe and Edinson Cavani.
"We always try to be aggressive, but of course when the result is 3-0 we know that things are more noticeable," he said.
"We know that if we don't make an almost perfect match here, you don't win. There's a lot of time to change this."
Madrid get a chance to respond when they make the trip to Sevilla in La Liga on Sunday.
The defeat was Real's biggest-ever loss in the Champions League under Zidane, the manager that won three Champions League titles consecutively during his first spell as manager.
And the French boss was quick to admit his side were outclassed on the day.
“PSG were superior to us in every aspect,” he told a news conference. “We scored two goals, but they have cancelled both. We must not think beyond, it has been a bad game.
“We lacked a lot of intensity. When you don’t have that, it's complicated!”