Porto boss Sergio Conceicao fears Chelsea's 5-2 loss to West Brom will have the Blues "more awake to danger" in Wednesday's Champions League quarter-final first leg.
Conceicao has warned his Porto players to be wary of the wounded Blues, who succumbed to a first loss under new manager Thomas Tuchel in the Premier League on Saturday.
"You know that Thiago Silva was sent off in the first half and that the game had a different course," said Conceicao.
"Chelsea until this last game had been extremely competent, they have not lost a game in the Champions League, they have the second-best defence in the Champions League and also in the English League.
"They are a competent team, and when these defeats happen it serves as a warning.
"If you want my opinion, I would prefer that they won the last game. Because these situations make the siren sound and make everyone more alert, more awake to danger, and I honestly don't like these defeats very much."
Porto will take on Chelsea without their suspended two top goalscorers, Sergio Oliveira and Mehdi Taremi, for Wednesday's last-eight first leg in Seville.
The Portuguese side battled past Italian giants Juventus in the last 16, and have been determined to keep highlighting their underdog status in the build-up to facing Chelsea.
"Obviously we look at Chelsea and see that these weekly tests are much more competitive than ours," said Conceicao.
"You can see that Chelsea's games are all extremely difficult, and that's an advantage for them.
"Anyway, when you enter the field, you don't think that we spent 25million Euros and Chelsea 250million.
"We will not think that Evanilson was the most expensive player, at 8million, and the most expensive player in Chelsea was (Kai) Havertz, at 80.
"On the field it's 11 against 11, with a strategy defined according to each team's idea of play.
"There may be one or another variant of the game to face this opponent specifically, but from there on there is nothing impossible. Everything is possible."
