Thiago Silva expressed concern about Brazil's form after a 1-1 draw against Senegal on Thursday left them winless in three matches for the first time since 2013.
Copa America champions Brazil took the lead against Senegal through Roberto Firmino after nine minutes in Singapore, but Famara Diedhiou fired home a penalty before half-time following Marquinhos' foul on Sadio Mane.
The Selecao, who drew with Colombia and lost to Peru in the previous international break, were unable to find a winner in the friendly international – Neymar seeing Alfred Gomis deny him a goal to mark his 100th cap in first-half stoppage time.
It could have been worse for Brazil had Mane's 20-yard effort with five minutes remaining not been kept out by the post, with Silva frustrated by their struggles in the final third.
"If I said I wasn't bothered, I would be lying. Unfortunately, in the last three games we have failed to show our best selves," Silva said in a post-match interview.
"I think we had the best chances but we were lacking a finish. It was a very equal game. We came up short on the last pass.
"We have to try to look at what went wrong and be more clinical with the last ball.
"Our opponents are more focused and studying our team. We have to get out of this rut."
Brazil will return to Singapore's National Stadium on Sunday to face Nigeria. Dani Alves suggested the heat, humidity and time zone played a role in a sluggish performance from the Selecao.
"I don't believe quality was missing. The opponents also played well and have good players," said right-back Alves.
"The circumstances were difficult. We have an 11-hour time difference [between Brazil and Singapore]; it's really hot. It's not an excuse, but it affects you.
"It is never easy to win. We are doing our best, but of course winning makes it easier to keep working."