Chelsea cemented their top spot in the Premier League on Sunday, with a win against Arsenal proving that they aren't to be easily beaten.
Eden Hazard's penalty gave the Blues a 1-0 lead, and a ninth Premier League strike from Diego Costa late on ultimately sealed the win, giving Chelsea all three points.
It was disappointment for Arsenal who didn't put in a bad performance, and when you consider their performance in comparison to the game last year they were significantly better. Still though, Arsene Wenger's wait for a win over Mourinho continues.
Both managers will definitely have things to focus on this week, here's what we learnt from the game.
1) Diego Costa is exactly what Chelsea needed
Lack of striking power was the reason why Chelsea didn't do so well last season, and with Demba Ba, Fernando Torres, Samuel Eto'o and Romelu Lukaku all leaving the club it was definitely time for a proper striker with a better goalscoring record to be signed.
Chelsea moved quick, and the £32 million signing of Diego Costa was soon completed. It's clear already he's the answer to their problems, with nine goals from seven Premier League games already we've seen that Chelsea's place in the table is a lot better than where they were at this stage last term with the Blues currently unbeaten.
It's fair to say they aren't winning these games only because of Diego Costa, yet with his arrival the Blues are better in attack indefinitely.
2) The Gunners do have a backbone
In the week when Joey Barton saw fit to criticise a lack of fight in the Arsenal squad; the team were determined to prove him wrong and ultimately put in 100% effort against a strong Chelsea side. Arsene Wenger's shoving of Jose Mourinho proved his exactly the desire of the Gunners and their efforts ultimately posed a harder threat to Chelsea. It was a very good game for the neutral spectator, and although they didn't have a shot until the 90th minute they still put up a stern test for Chelsea.
It made good viewing, and in a way Barton could've been proved right in previous matches. Yet today was different, and it wasn't the Arsenal who'd try to sit back and look for other people to do the hard work. Today wasn’t exactly a good game for fans, but at least it was more of an acceptable failure.
3) Injuries have hit again for Arsenal - as always
Just like every year Arsene Wenger has injuries to contend with once again, and midfield regulars Aaron Ramsey and Mikel Arteta were missing from yesterday's starting XI ultimately weakening the Gunners in the middle of the park leaving Wilshere as the strongest link.
We thought that this year would be different, the year that Arsenal would be going for the title especially after the marquee signing of Alexis Sanchez. Just as we thought there'd be nothing stopping them, suddenly the usual problem bites again. Although Arsenal didn't lose the game because of this, still it is a worry for boss Arsene Wenger. It appears that they don't have enough quality in their squad to cover injuries.
Perhaps in January he may have to sign a few reinforcements?
4) Flamini just isn't what he used to be
In a game that without the likes of Aaron Ramsey and Mikel Arteta missing for the Gunners it was time for Flamini to step up to the plate and put in a performance of a lifetime, however it's clear he didn't take his chance.
Normally Flamini would be the tough-tackling member out of the bunch of Arsenal lads, and with his experience you'd expect him to be taking the game by the scruff. However, the Frenchman simply didn't cut the mustard, and perhaps struggled to keep pace with the game which was very intense. Now I'm not criticising him as a player, I just feel that he had a very bad game today.
Back in the day when he used to be a member of the Arsenal squad he'd be providing a real protection to the back four, however on Sunday he was non-existent, with the defence being breached numerous times.
5) Chelsea have all the title credentials
After fixing the frailties of last season finally we can see Chelsea in a new light, and it's hard to see just who will beat the Blues. The signings of Fabregas, Costa and bringing back Thibaut Courtois all make Chelsea a very strong team.
It's clear it's going to be Jose Mourinho and Manuel Pellegrini challenging for the title come May and with City already looking weak in a few games throughout this campaign it looks as though it could be Chelsea's to lose. Chelsea proved on Sunday that even though they may not put in top performances every game, they are very good at grinding out the wins and don't like losing. Just who will challenge the Blues?
If Costa can keep firing and try to avoid injury, Cesc Fabregas can keep grabbing the assists, Terry and Cahill can stay firm in defence and Courtois can keep the clean sheets then Chelsea look an unstoppable force.