Yoane Wissa scored a stunning bicycle kick to give Brentford the lead against west London rivals Chelsea.
Nicolas Jackson had given the Blues a lead with a first half header before Mads Roerslev's equaliser five minutes after the break.
On the 69 minute mark, Reguillon delivered a cross into the box and Chelsea failed to clear their lines properly before Wissa pounced with a super bicycle kick to put the Bees 2-1 up.