Chelsea aren't title contenders if you believe the man picking their team. Days like this might just give him second thoughts.
Granted, the defence is a little loose at times. Maurizio Sarri says that himself and Cardiff's goal to take the lead in this game rather underlined the point.
But the sheer brutality of the retaliation made another, which is that they are quite capable of dishing out a kicking when the mood takes them. Of course, Cardiff are Cardiff, and impressive as they were at times in this match, you would expect them to swallow a few shoes away at Chelsea.
And yet September seems frightfully early to write off a team containing Eden Hazard, who scored a hat-trick here. A little premature to dismiss the title credentials, when Sarri made the perfectly sound decision to put Willian on the bench and then watched him win a penalty and slap a goal into the top corner in what was barely a 20-minute cameo.
That is a signifier of depth and five wins from five is a signifier of strength. The fixture have been kind, we all know that. Only Arsenal in those opening games serve as meaty opposition, and the truer gauge of where they stand will come from the league meeting with Liverpool at the end of this month.
But it is cynical in the extreme to argue with a perfect record, even if instinct tells you that Manchester City have the best squad and Liverpool stand as the biggest threat to their crown. Those instincts would not be misguided, particularly with Chelsea lacking a legitimately brilliant centre forward.
But if ever a team deserved the benefit of a doubt, it is one that wins its first five games. To that end, Sarri is just the fourth man ever to do so in his first five in the Premier League.
So far, so good, then. And this was another of those matches when he got his big calls right.
The two changes he made to his line-up here both paid off. Olivier Giroud came in for Alvaro Morata, a replica of the second-half substitution that turned the game against Bournemouth before the international break and a hint that quite possibly Sarri has a few of the same reservations about Morata as Antonio Contre.
The other alteration saw Pedro given a start ahead of Willian and with three goals in four games before this one that was a reasonable reward for form. In each case, the switches were quickly and firmly vindicated.
In the instance of Giroud, the benefits were tactical as well as technical. Cardiff sat deep, understandably, and Morata just isn't the back-to-goal kind of guy you need for that sort of scenario. Giroud wins his share of high balls, so he can do that shift and was an option on those occasions which called for aerial attacks. Inside seven minutes he put a header onto the roof of the net to illustrate the point.
But Hazard's two first-half goals showed how much more Giroud can offer when his form is right. For the first, at 1-0 down, the Frenchman was the wall in a lovely one-two, playing the return pass that committed Joe Bennett and set Hazard on his way to goal.
Granted, it was the brilliance of Hazard that turned a chance into a goal, considering the Belgian first beat Bennett to the ball to clear and then rolled a delightful finish across Neil Etheridge to score. But the touch of Giroud showed once more the knack he has for linking play in this team.
His lay-off for Hazard's second, on 44 minutes, was another example. The touch was again quite brilliant, taking a low ball from Pedro on the left and setting it perfectly for Hazard to crash through the crowd on the line.
For Pedro's part, aside from his contribution to that second goal, there were two first-half strikes that almost made for lovely goals, and a third early in the second, only for one to go a shade high and the other two to go fractions wide. Fine margins, but another fine performance on the right. With him and Willian to choose from for one spot, Sarri is truly spoiled.
His concerns, by his own admission in the past few days, come at the other end, with his defence. Previously the vulnerability has come from Sarri's high back line and the space he gives up in behind his four, but here the issues came in facing high balls and set-pieces.
Even before Bamba put them in front, he had enjoyed the luxury of a free header in front of Kepa Arrizabalaga. He put that one wide. His goal offered no such escape and will give Sarri a bit to consider in the analysis.
Joe Ralls had floated a reasonably unthreatening free-kick to the edge of Chelsea's area, but Marcos Alonso lost the aerial duel to Sean Morrison, whose header went back across goal. Jorginho had been tasked with following Bamba, but lost track of perhaps the biggest man on the field and a goal was the consequence.
So there is work for sarri to do. But that, really, was the limit of Cardiff's threat. True, they played well, got a lead, punched above their financial weight, but almost immediately were faced with a bigger beast, as demonstrated by Etheridge making two very good saves to deny Mateo Kovacic in the two minutes following Bamba's goal. Thereafter, Hazard had his two goals and Chelsea were where they needed to be.
There was a brief threat after the break when Bobby Reid pulled a chance wide, but Hazard's hat-trick killed off the resistance, with his penalty converted after Willian was brought down by Bamba.
Willian wrapped it up with a superb curler into the top right corner from the edge of the area.
PLAYER RATINGS, LEAGUE TABLE AND MATCH ZONE
C helsea (4-3-3): Arrizabalaga 6; Azpilicueta 6, Luiz 6, Rudiger 6, Alonso 6; Kante 7, Jorginho 6, Kovacic 6.5 (Barkley 50, 6.5); Pedro 7 (Willian 68, 7.5), Giroud 7.5, Hazard 8.5 (Zappacosta 84)
Subs not used: Drinkwater, Caballero, Zappacosta, Christensen, Morata.
Manager: Maurizio Sarri 7.5
Goalscorers: Hazard 37, 44, 80 (pen), Willian 83
Cardiff (4-4-2): Etheridge 7; Manga 6.5, Morrison 7, Bamba 7, Bennett 6; Camarasa 6, Ralls 6.5, Arter 6 (Richards 46, 6), Hoilett 7; Reid 6.5 (Paterson 71, 6), Ward 6 (Madine 77).
Subs not used: Peltier, Zohore, Cunningham, Brian Murphy.
Manager: Neil Warnock 7
Goalscorers: Bamba 16
Referee: Jonathan Moss (County Durham) 7
Olivier Giroud turned provider for Chelsea's second as Eden Hazard scooped in. CLICK HERE for more from Sportsmail's Match Zone.