Less than two weeks after concerns for Ryan Mason following a collision in the penalty box at the Shed End of Stamford Bridge and Hector Bellerin was on the floor, concussed, in roughly the same spot.
This time, thankfully, the injury was not so serious. Mason was rushed to hospital where he required emergency surgery on a fractured skull.
Bellerin was back on the Arsenal bench in time to see the second-half Chelsea complete the victory, not something which will have helped ease his headache.
Nor is it likely to soothe the mood of Arsene Wenger, banned from the touchline and seated high in the East Stand.