Arsenal have "great quality" and a "class manager", according to Frank Lampard, who has warned his Chelsea players not to underestimate the "dangerous" Gunners.
Chelsea picked up their seventh win of the season to move up to fifth in the Premier League standings on Monday night, beating London rivals West Ham 3-0 at Stamford Bridge.
The Blues bounced back from successive defeats against Everton and Wolves to close the gap on first-placed Liverpool to six points, capping a generally strong start to the 2020-21 campaign.
In stark contrast, Arsenal have slipped to 15th in the top-flight after losing eight of their first 14 fixtures, with their winless run extended to seven matches after a 2-1 defeat to Everton at Goodison Park at the weekend.
Mikel Arteta's side are in real danger of being dragged into a relegation battle if results don't start to improve, and they will head into a meeting with Chelsea at Emirates Stadium on Saturday as heavy underdogs.
Although Lampard was pleased to see his team improve on their impressive recent record in London derbies with a comfortable victory over West Ham, he will be taking nothing for granted when another cross-city rivalry is renewed on Boxing Day.
The Chelsea boss insists Arsenal are a far more formidable outfit than their current league position suggests, and he has no doubt that Arteta will have his players fired up for a game they can ill-afford to lose.
“We've been in decent form [in London derbies] but I don't think we should be taking Arsenal at face value,” Lampard said after the Blues' clash with West Ham.
"With Arsenal, I see a team of great quality, a class manager who are in a tough moment.
"That's a really dangerous combination to go against, so we have to prepare right."
The 42-year-old head coach added: “The league is so tough and we are seeing results every week that might surprise some. It’s hard for most teams to sustain results that might be expected in different seasons and there’s a combination of reasons for that.
"It can be tough [playing your rivals]. They're all very challenging games, we saw that on Monday, with West Ham and obviously [Michail] Antonio not being around changed the element of it slightly.”