“My opens are awful,” Keith Hernandez says. “I can’t do an open.”



It’s about 90 minutes before SNY will go on the air last Wednesday night, for the middle game of a three-game set with the Cubs. Hernandez has just praised the spontaneity with which he, Gary Cohen and Ron Darling approach each Mets broadcast — the unscripted way everything comes together, like free-form jazz, to steal the trio’s preferred metaphor.



Everything, that is, except the open.



“I’m always nervous in the opens,” he continues. “Ronnie is smooth as silk. I’m just glad when they’re over.”



When that light blinks on right at 7 p.m., Hernandez talks about the decision to play Juan Lagares in center field with third baseman Todd Frazier sitting: “I think this is more about Mickey Callaway with a team only scoring 11 runs in the last five games and Frazier slumping, he’s trying to...