Brazil's defeat to Cameroon is "a warning signal" they must heed ahead of the World Cup knockout rounds, says Dani Alves.

The Selecao fielded a much-changed side in their final Group G match, with progression to the last 16 already secured.

But a late Vincent Aboubakar finish condemned Tite's side to a shock 1-0 loss in Lusail, to check Brazil's momentum heading forward.

With a last-16 tie against South Korea now confirmed, veteran defender Alves - who skippered his nation against Cameroon - believes it is a reminder that there is no safety net now for his side.

"It's a warning signal," he said. "There is no weak rival. Here is the lesson, we need to stay switched on throughout the game. One detail and it's over.

"We end today with the feeling that a beautiful day slipped through the hands of us players who weren't playing much."

Brazil arrived at Qatar 2022 as the pre-tournament favourites, a record enhanced after two strong opening performances against Switzerland and Serbia prior to the defeat to Cameroon.

Despite the likes of Germany, Belgium and Uruguay tumbling out of the competition, Brazil face a difficult path to the final should they get past South Korea, with Argentina and the Netherlands among their potential semi-final opponents.