Cech, 35, then saw Glenn Murray's header squirm under his body to double Brighton's advantage less than 20 minutes later.
So which players disappointed most for the Gunners this afternoon? Arsenal's season fell to a new low with a fourth straight defeat in all competitions, which also left them 13 points outside the Premier League's top four with just nine games to play.
The problems facing Wenger are obvious, with the under-fire Frenchman unable to inspire an underperforming squad into producing the level of performance required to ease some of the pressure being piled on his shoulders.
They now prepare for a crucial game in the Europa League in Milan on Thursday as it looks like being their only route into the Champions League for next season.