49ers guard Joshua Garnett needs knee surgery, out a month

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The 49ers were already undergoing significant structural changes, now the injuries are starting to pile up.

The same day they lost linebacker Malcolm Smith to what could be a serious pectoral injury, they found out they’re going to be without a former first-rounder for at least a month.

According to Matt Maiocco of NBC Sports Bay Area, guard Joshua Garnett probably won’t be ready for the start of the regular season because of a knee problem that requires surgery. It’s not believed to be an ACL problem, but the 2016 first-rounder is expected to miss some time.

“I know there’s some stuff in his knee we’re probably going to have to clean up,” 49ers coach Kyle Shanahan said. “I don’t think it’s anything long-term, but it’s going to be a little bit of time.”

Garnett was a bit of a surprise first-round pick last year by then-coach Chip Kelly, but he started 11 games. With him out, the 49ers have veterans Zane Beadles and Brandon Fusco at the guard spots.