49ers rookie Nick Martin focused on learning from rough NFL preseason debut

SANTA CLARA — Sitting at his locker Saturday night, 49ers rookie linebacker Nick Martin already was watching video of his first NFL preseason game.His assessment was succinct.“I’m taking it on the chin, and making sure I learn from it and get better,” Martin told NBC Sports Bay Area following the 49ers’ 30-9 loss to the Denver Broncos at Levi’s Stadium.Martin had a rough night. And he was well aware of it.When asked if there was a play he would like to have back, he could not pick just one.“There were a few of them,” Martin said. “Definitely, yeah, a few I wish I could have back. But that’s life. You wish you could have some moments back. You just got to learn from them and make sure you capitalize on them the next time.”Martin’s most difficult stretch came in the third quarter when he missed back-to-back tackles on Broncos second-year running back Blake Watson. The first resulted in an 18-yard gain on a running play. The next was a 16-yard pass play.A short time later, Martin missed another tackle on Watson, but...