Rafael Benitez was not fully convinced by his Chelsea players despite their 3-1 FIFA Club World Cup semi-final win over Monterrey in Yokohama on Thursday.
The European champions were served by goals from Juan Mata, Fernando Torres and a Darvin Chavez own-goal before Aldo De Nigris struck in injury-time for the Mexicans.
Despite the relative ease of the scoreline, Benitez feels his Blues side were quite slack in their play and has urged them to buck up before Sunday's final against South American champs Corinthians.
"I'm not very happy with the goal we conceded," he said.
"We won, which is fine, but still these little things can make a difference in a final, for example.
"When I talk about a winning mentality, always I talk about little details making the difference.
"The team has to think about winning, winning in style and not conceding because the goalkeeper (Petr Cech) likes clean sheets.
"They have to keep their concentration right to the end of the 90 minutes. That's what they need to do."
Chelsea takes on Brazilian giants Corinthians on December 16 in the decider after the third-place playoff between African title-holders Al-Ahly of Egypt and Monterrey.
