It was high risk and no reward for Chelsea on Wednesday night.
They had gone toe‑to‑toe with the best team in Europe on their own turf for 74 minutes, but after Filip Jorgensen's mistake, that positive display unravelled into a whimpering collapse.
A lack of concentration, ill‑discipline and, perhaps, a shortage of real quality at the highest level left Chelsea well beaten.
When it came to concentration, Jorgensen was the prime culprit. Playing in arguably the biggest game of his career in the last 16 of the Champions League, he threw away his opportunity to stay as number one ahead of Robert Sanchez.
It could well be that neither goalkeeper is good enough, with Robert Sanchez having struggled in two of recently appointed head coach Liam Rosenior's first three games against Arsenal, which ultimately got him dropped.
But Jorgensen was far from the only one at fault. One of the star performers this season, captain Reece James, stumbled when challenged by Senny Mayulu for the fourth goal, while Chelsea were simply played through, leaving several players out of position for the fifth.
Even Cole Palmer squandered a crucial chance 14 seconds before Dembele scored a more difficult one on the counter‑attack.
And, to highlight Chelsea's indiscipline, Pedro Neto pushed over a ball boy after the fourth goal, sparking a mass altercation between both sides.
The Portugal winger attempted to repair the damage after the match by giving the ball boy his shirt, but he risks facing further Uefa action.
It was another damning indictment of a team that can be brilliant at their best but implode at their worst.
It came against PSG, one of the few teams younger than Chelsea in Europe's top‑tier competition, showing that success is possible with a youthful squad.
However, PSG proved on the night they have cooler heads, greater quality and are everything Chelsea want to be but struggling to become.
