Sergio Conceicao fears Chelsea's shock loss to West Brom could work against Porto heading into the first leg of their Champions League quarter-final tie.
Chelsea had not lost under Thomas Tuchel before a stunning 5-2 home reverse on Saturday, a result that led to the Blues dropping out of the Premier League's top four.
Defender Thiago Silva was sent off shortly after his side had taken the lead against relegation-threatened opponents, with his dismissal leading to a dramatic collapse that Tuchel admitted in the aftermath was "tough to digest".
Porto, therefore, are wary of a possible backlash from that result in Seville, the venue for both games between the teams due to the travel restrictions in place during the coronavirus pandemic.
"You know that Thiago Silva was sent off in the first half and that the game had a different course," said Conceicao, whose side will be listed as the home team on Wednesday.
"Chelsea until this last game had been extremely competent, they have not lost a game in the Champions 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. 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."
Rather than read too much into the West Brom game, Conceicao highlighted how Chelsea had impressively overcome Atletico Madrid in the last 16, winning both legs without conceding a goal.
He also referenced his opposite number's penchant for tinkering with tactics to suit each match situation, something he says Tuchel also did during his time in charge at Paris Saint-Germain.
"In the analysis of Chelsea, practically that last game wasn't considered," the former Portugal international said.
"There were other games that they played before that, namely those in the Champions League against Atletico Madrid, but this one [against West Brom] did not enter [our analysis].
"Tuchel is a coach who is capable of changing even if he wins, while in France he did the same at PSG. Play with two men behind the striker or play with two men in front, as in the first round with Atletico. It is up to us to analyse that dynamic.
"I saw the last game they played, but we did not present images to the players of that game."
Porto made it through to the last eight at the expense of Juventus, but veteran centre-back Pepe made clear the players will not dwell on their Turin heroics and instead focus on the task in hand - getting past Chelsea.
"The Juventus match is already in the past. This is the important one now. We must show a lot of passion and humility and work as a team," said the defender, a three-time Champions League winner during his time at Real Madrid.
"We have prepared well. Nothing is certain in football, but I hope we will be the team that our fans expect. We respect Chelsea. It will be difficult, but we want to win this tie."