Roberto Di Matteo's team went down 3-1 at the American Express Community Stadium on Saturday despite taking the lead.
It was Chelsea's third successive defeat in pre-season friendlies, but Poyet refuses to write off the European champions' chances of defeating Manchester City at Villa Park.
"I won't be surprised if they come out and are unbelievable, because I know how those players are," the Uruguayan told Chelsea's official website. "They will give something extra."
Poyet also looked back on Brighton's performance against Chelsea at home on Saturday but did not get carried away.
"For us this was the biggest game ever, but for them it was just an extra game so it is not the same," he opined. 'I'm sure they will get there.
"I can see what he (Di Matteo) means (when he says Chelsea lacked intensity), but I am sure they will get it back because they are world-class players, and as soon as they are playing for something it is going to be different for sure.
"We tried to make it difficult. Normally a friendly game is very open but we defended deep with nine players behind the ball. Any good team is difficult to beat when they get tight and play for each other, and it's an important game for them."
Chelsea will begin their Premier League campaign with an away game against Wigan Athletic on Sunday, August 19.