​Chargers quarterback Justin Herbert was on the field for Thursday night’s preseason game against the 49ers.But if you blinked, you would’ve missed it.Herbert’s exhibition debut with Mike McDaniel as his play-caller lasted just three snaps, with the Chargers going three-and-out on their first offensive possession.Omarion Hampton lost a yard on the first play from scrimmage. Then Herbert completed a 9-yard pass to tight end Charlie Kolar while rolling to his left. But on third-and-2, Herbert’s downfield pass to Ladd McConkey was well off and incomplete.With the ball at the Los Angeles 43, the club elected to punt.Trey Lance came in to relieve Herbert at quarterback on the Chargers’ second drive later in the first quarter.