Mauricio Pochettino has alluded to an unspecified incident which "affected the team" ahead of Chelsea's 1-0 win over Fulham.
Cole Palmer scored the only goal, from the penalty spot, to earn west London bragging rights.
The result moves Chelsea up into eighth, ahead of Newcastle and Manchester United before the pair play later in the weekend.
But Pochettino believes his players were somewhat hampered in the opening stages, though insisted it should not be a concern to fans.
"The first half wasn't the first half that we planned, he said. "Something happened before the game that I cannot explain. I think that it affected the team a little bit.
"We started the second half really good. I think we played really good football for 30 minutes and should score another goal or one or two and kill the game.
"When the game is open like this and you don't kill the game, always in the last minutes we concede a few actions, set pieces and wide free kicks and they have good potential in these situations.
"We defended well and I think it was good for us to suffered a bit at the end. I think this type of game will make us grow and to build confidence in the way we are working."
When pressed about the incident, he simply added: No, no. Nothing. Nothing, sorry. It's nothing big. Small details that sometimes effect the team.
"You need to know that something affected the performance in my opinion but it's not important for you or our fans to know, sorry."
Pochettino also moved to clarify quotes from Friday in which he appeared to call on Chelsea to buy another striker should Christopher Nkunku's injury problems.
But Pochettino said he was misunderstood.
"I never said we need a centre-forward," he said. "I said we are working like other clubs, trying to assess and see the situations that can appear. I never said we need to add another player."
Palmer scored a crucial spot-kick just before half-time to earn a third Premier League win in a row.
Pochettino accepted, however, that Malo Gusto could have been sent off for a bad challenge on Willian, adding: "If I was in his place, I want to tell you it was a red card.
"I understand. Sometimes it's for you, sometimes it's against and this type of situation, the view of the referee is different. What I can say is the action and they gave a yellow card. It was good for us."
