John Saunders -- Wife Called 911 ... Found Him Unresponsive

' wife found the ESPN legend unresponsive and not breathing early Wednesday morning and called 911 ... law enforcement tellsJohn Saunders TMZ Sports.

Hastings-On-Hudson Police Chief Visalli tells TMZ Sports ... emergency responders raced to Saunders' New York home around 4 AM -- but were unable to resuscitate him. He was pronounced dead at the home.

We're told a detective was sent to the home -- but found nothing suspicious. Since there were no signs of foul play, the medical examiner rejected the case.

We're told the exact cause of death is still unknown.

Saunders was 61.