Inattentive. Not ready; missed an important opportunity (‘Wheel’ (sometimes used a switch) demonstrates the steering wheel in a vehicle or on a boat or any circumstance where one is in control of a process; this phrase implies that due to a lack of alertness, the one in control missed an important change.  (Compare to Sleeping on the job.)

“Training young people for baseball is difficult because they always daydream. When a ball does come to outfield they are always asleep at the switch and miss catching it.”