The Blues sit nine points ahead of the Gunners at the top of the Premier League table, despite having lost 3-0 at the Emirates back in September.
Arsene Wenger’s men suffered a damaging blow to their title bid on Tuesday as they fell 2-1 at home to Watford.
And a win today (12.30pm) at Stamford Bridge would realistically see Chelsea end Arsenal’s hopes for another year.
Thibaut Courtois insists Chelsea have a stronger mentality than Arsenal
Goalkeeper Courtois was part of the Chelsea team that crumbled last season on the back of title glory.
However, he claims the squad never lost its talent and have proven that their failings were due to mentality.
"People talk about our improvement this season, but you could also ask why we went from being champions by eight points to finishing tenth last season," Courtois told The Times.
"It's not just a case of last year we were so s***, this year we're so good. We were always a good team, but after winning the championship our mentality dropped.
“We maybe thought that everything was easy, but in the Premier League there are no easy games. We lacked intensity at the start and it was hard to pull out of it.
"This year we've had a new mentality, particularly with the new coach coming in. He's brought the winning mentality and hunger to win again. He's very hungry and we can feel that in training, he's very close on us every single day.
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Chelsea v Arsenal combined XI: Which stars make the cut in our team?
Fri, February 3, 2017
Express Sport compiles a star-studded XI of players from Arsenal and Chelsea ahead of their Premier League clash on Saturday (12.30pm)
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Which Arsenal and Chelsea stars make it into our combined XI?
Arsenal players will have to prove their mental strength at Stamford Bridge today
Arsenal are good, but their performances are a bit irregular
“There's no let-up. He's on to us that we have to win, win, win. After we lost at Arsenal in September the players got together and said, 'We cannot have a season like last year, we have to change something and work harder.' Our mentality changed.”
On today’s opponents and the game’s implications, Courtois added: ”Arsenal are good, but their performances are a bit irregular. I think we have a stronger mentality.
“This game won't decide the Premier League, but if we win and go 12 points ahead of Arsenal a lot of things have to happen for us not to be champions. Victory would send a signal to other teams that we won't drop many more points."