Chelsea saw their advantage over second-place Tottenham cut to just four points after Sunday's surprise 2-0 defeat at Manchester United.
The Blues have now lost two of their last four Premier League outings, while Spurs are enjoying a seven-game winning streak.
And while Luiz is aware of Tottenham's form, the Brazilian defender insists Chelsea are not top of the table for no reason.
The 29-year-old centre-half said: "Tottenham are playing very well but also we are top of the table for a reason.
"We still have to play a lot of football, so we need to look forward and play the next games."
Chelsea were dealt a huge blow on the day of their Old Trafford clash after Marcos Alonso was ruled out through illness.
The left wing-back has been crucial in Chelsea's rise to the top, but Luiz insists the Spaniard's absence was not to blame for their defat.
Luiz added: "This kind of thing can happen, he felt a bit sick so that is why we had to change.
"It didn’t affect the game because Marcos did not play, we lost because we did not play very well and it was not the Chelsea like before and sometimes this happens.
"We didn’t play well, Manchester United played better than us and they deserved to win."