Arsenal and Chelsea have been reduced to also-ran status by Manchester City's blistering pace in the title race, but there is still a lot to learn when the London rivals clash at the Emirates Stadium on Wednesday.
With champions Chelsea lagging 14 points behind City and Arsenal sitting six points outside the top four, there's clearly plenty of room for improvement in both teams.
Here AFP Sport looks at the problem areas for Arsenal manager Arsene Wenger and Chelsea boss Antonio Conte:
Rebels with a cause
After boldly deciding against selling Alexis Sanchez and Mesut Ozil before the start of the season, Wenger has seen his gamble backfire as speculation about Arsenal's contract rebels has been a constant distraction.
Sanchez and Ozil are out of contract at the end of the season and have refused to sign new deals, raising the possibility that both could be sold in January to avoid losing them for free in June.
Making matters worse, Sanchez, who was frustrated by Wenger's refusal to let him join Manchester City in August, has pouted his way through the campaign — frustrating players, coaches and fans in the process.
City, Paris Saint Germain and Real Madrid are all contenders to rid Wenger of the Sanchez problem, but the damage has already been done.
German midfielder Ozil, wanted by Manchester United and Barcelona, has been less overtly troublesome, but his inconsistent performances have hardly suggested complete commitment to the cause.
No wonder former Arsenal star Martin Keown said: "Wenger puts so much trust in his players but Sanchez and Ozil have been overindulged.
"You wonder where they would be had these two been fully committed for the whole season."
Although Alvaro Morata has been a qualified success in his first season at Chelsea, the former Real Madrid striker has been virtually the sole goal threat for Conte's men.
Morata has scored 12 times, but only twice in his last seven league games.
With 39 league goals this season, the Blues have scored less than the other teams currently in the top four.
Solving that problem has been impossible for Conte because Belgian forward Michy Batshuayi, the main back up for Morata, has scored only twice in the league and hasn't netted since October.
Conte is certain to push for a new striker to be signed in the January transfer window, with Inter Milan's Mauro Icardi and Sassuolo's Domenico Berardi among potential targets.
Having leaked 26 league goals this term — more than any other team in the top seven — Wenger once again finds his failure to fix Arsenal's leaky defence is undermining his side's ambitions.
While Wenger has switched formations from a back three to a back four, changed defensive personnel and tried to protect them with different holding midfielders, the root cause of Arsenal's Achilles heel remains philosophical.
Wenger's commitment to an attacking game-plan which relies on a smooth-passing style earns plenty of plaudits from the purists.
But the Frenchman's tactics often leave Arsenal's full-backs out of position and his midfielders too far forward, while his reliance on diminutive playmakers allows opponents to bully the Gunners.
Search for motivation
Manchester City's sensational first half of the season has left Conte with the tricky task of keeping his players motivated when it seems they have little to play for in the league.
At times, Chelsea were fatally unfocused when they faced opponents who didn't immediately inspire respect and the result was lethargic and damaging defeats at lowly Crystal Palace and West Ham.
Conte is a notoriously demanding coach and there has been growing speculation that his players are tired of Italian's intense training sessions.
Balancing a need to remain in charge of his stars, while also keeping them onside could be a challenge for Conte given the lack of drama in the title race, but he has no intention of changing his style.
"You must always have a great desire to do this job. My wish for myself is to continue to have this desire for many years," Conte said.