Manuel Pellegrini says West Ham will not make excuses after they lost 3-1 to Tottenham in the Carabao Cup on Wednesday.
The Hammers were the better side during the first half at the London Stadium, but a double from Heung-Min Son and a goal from Fernando Llorente shortly after Lucas Perez's consolation saw them exit the competition.
Pellegrini believes mistakes cost West Ham their place in the quarter-finals, saying: "When you lose a goal like that and the game it is not good to try and find excuses.
"The first goal also came after we dominated the game and they scored. After that we made mistakes, for the second goal as well.
"It was important to continue in this cup, but we couldn't. But we must always think that the Premier League is more important on Saturday."
There were two incidents of fans on the pitch during the game - one of whom was stopped by Angelo Ogbonna - and Pellegrini commended the behaviour.
"I don't think it is good for football," he added. "One of the most important things the Premier League has is, it is always organised so I think that it is not good for football."