Spurs were shocked by their London rivals at White Hart Lane on Sunday, conceding three goals in the second half to lose 3-0, and the Belgian is keen to ensure that they improve their concentration.
"You see from the top teams that, if they want to be champions, you have to win these small games," he told reporters.
|6/4||Tottenham are 6/4 with BetVictor to finish in the Premier League top four
"It's easier to play against the top teams for the motivation but, if we want to be a top team, we need to be concentrated for these kinds of games. It's a mental thing, so we have to talk as a team and make sure we’re all focused.
"We have a lot of players and we can change the team very quickly, so everyone knows it can be a difficult season.
"When we play against sides like West Ham, we have to be very careful. They have a different kind of style but this is the Premier League and you have to be used to these kinds of days, so it is a shame that we weren't prepared.
"In the second half we looked very tired and we didn't have too much passion. You have to win these kinds of games if you want to have a good season, so it's a shame."