Blindside

lado ciego

(motor vehicle/train/tram driver's field of blindness)

ampayar con la guardia abajo

(catch off guard)

atacar por el lado ciego

(To attack (a person) on his or her blind side)

cachar inadvertidamente

(catch off guard)

coger por sorpresa

(catch off guard)

desconcertar

(catch off guard)

pillar desprevenido

(catch off guard)

sorprender

(catch off guard)

tomar por sorpresa

(catch off guard)