SNY tonight will debut the documentary “He’s Keith Hernandez” at 6:30pm ET, "part of the leadup to the Mets retiring" Keith Hernandez's No. 17 on July 9. The film is an hour long including commercials, "so it is a Cliffs notes version of his eventful life and career, with a rich mix of video footage ranging from his Little League days to his appearance on 'Seinfeld' in 1992 to his work as an SNY analyst since 2006." But the "emotional highlight is the exploration of his relationship with his 2 ½-years-older brother, Gary, who is interviewed in the film and played a key role in Hernandez’ development as a person and player" (NEWSDAY, 6/29).