Most right-thinking Arsenal fans have a love/hate relationship with Hector Bellerin. They love it when he's out of the team and hate it when he's in it.
As desolate as the Spaniard may be defensively, however, few expected him to be troubled on Wednesday. Facing him for the International Champions Cup game against Chelsea was Calum Hudson-Odoi, a player most had never heard of.
They knew his name soon enough. The England youth star was magnificent on the left of a three-pronged attack, eviscerating Bellerin and forcing him into conceding a penalty.
"He will stay with us for all the season," Maurizio Sarri smiled when asked about plans for the 17-year-old.
It's no wonder. Under a new manager and a new system, Hudson-Odoi could be a devastating addition to the first team.
Many players have pace and skill. Hudson-Odoi, though, has shown real intelligence and, crucially, an end-product throughout Chelsea's pre-season programme. Before his scintillating display in Dublin, he had already laid on an assist against Internazionale.
Sarrismo, the intensive system which Napoli used to such devastating effect last year, depends on rapid wide forwards and reflexive passing exchanges between the lines.
The trio of Lorenzo Insigne and Jose Callejon, either side of Dries Mertens, were guaranteed starters because they fitted the mould that the tactic required.
Hudson-Odoi meets the same archetype, and with Willian's future still to be decided, the youngster could find himself playing a key role in the forthcoming campaign.
It is great news for Chelsea fans, who can look forward to an enthralling season after a summer that was dominated by Antonio Conte's demise. Hudson-Odoi won't face disasters like Bellerin every week, but if you're this good this young, you don't care who you line out against.
How much can he expect to play?
It would be foolish to expect Hudson-Odoi to be anything more than a depth squad player next season and the worry is that he struggles to get game time ahead of the more experienced players in the squad.
What would be the point in him making the occasional 15-minute cameo?
However, if Chelsea do eventually sell Willian and even Eden Hazard - Hudson-Odoi could be a readymade replacement.
If he can impress like he has in pre-season for Chelsea in the Premier League, then Sarri will have no qualms in giving him a proper run in the first team.
Expectations should be limited for a teenager, but the Blues look like they have a star in the making. Now they must make sure that they develop him properly.