Chelsea boss Antonio Conte says last September's 3-0 defeat against Arsenal has to be cancelled out when the two teams meet later on today at Stamford Bridge.
The Blues are 9 points ahead of the Gunners, eager to open a 12-point lead at the top of the table.
But the Italian says his players have to pay "great attention" if they are to take all three points from today's game.
"This defeat seems far away, but it's important to remember the defeat against Arsenal," Conte explained.
"It was a bad defeat, 3-0 in the first half. In my mind this defeat is always present. I hope also it is in the mind of my players because tomorrow this game will be very difficult.
"A lot of things have changed now. For sure we are a team, we want to have a good game against Arsenal and try to win.
"At this moment it's very important to exploit this momentum. We are in good shape; we are playing good football with intensity. Now we have a good opportunity to show this.
"We play at home, we have our fans to push us a lot, but for sure we must pay great attention.
"I watched their game [against Watford] and sometimes the final result doesn't tell the truth. Arsenal were unlucky. Watford played a really good game. Arsenal had a lot of opportunities to score a goal and win the game.
"They are in good shape and good form, and the result is a strange result.
"I repeat: if someone thinks the league is finished, I'm not so sure. I want to have this right tension. In the past I fought to win the title, and I know we must pay great attention.
"There are 15 games to play and there are a lot of great teams behind us."
