Fans wave in hopes of getting a free t-shirt during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Fans wave in hopes of getting a free t-shirt during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

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John Lynch, 49ers general manager, at left, and Kyle Shanahan, 49ers head coach, talk during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)



Matt Breida warms up during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Brian Hoyer passes during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Reuben Foster walks through a play during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)



Players prepare to run a play during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Reuben Foster, at right, greets Cole Hikutini during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Tank Carradine warms up during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)



Coach Kyle Shanahan oversees San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Players stretch during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Brian Hoyer passes during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)



Pierre Garcon looks up at the stadium during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Navarro Bowman warms up during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Brian Hoyer passes during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)



Mike Bongato, 42, of San Francisco, at left, Ricardo Lopez, 34, of San Jose, and Andrew Moreno, 23, of Salinas, show off their signed Navarro Bowman jerseys after San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Matt Barkley passes during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

Brian Hoyer takes a snap during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)



The Gold Rush cheerleaders prepare to take the field during San Francisco 49ers practice at Levi's Stadium on Saturday, Aug. 5, 2017, in Santa Clara, Calif. (Jim Gensheimer/Bay Area News Group)

SANTA CLARA – Excitement from the 49ers’ most successful public practice ever at Levi’s Stadium was tempered Saturday by injury news about two starters: inside linebacker Malcolm Smith and former Stanford guard Joshua Garnett.

An ensuing MRI exam revealed that Smith sustained a season-ending torn pectoral muscle, the 49ers confirmed after practice. Smith’s exit could clear a path for rookie star Reuben Foster or energetic veteran Ray-Ray Armstrong to become the starting weak-side linebacker next to NaVorro Bowman.

Garnett did not practice because of a knee injury that is expected to require “clean out” surgery, although not of a season-ending variety.

Taking those injuries into account, here are the top three things we learned after Saturday’s practice that attracted 25,319 fans:

1. Next-man-up time. Smith and Garnett are the first two starters to sustain significant injuries impacting the season-opening lineup Sept. 10. So how are their replacements faring?

Foster, a first-round draft pick, has been this camp’s play-making sparkplug, albeit typically on the second- and third-string units. Foster found himself Saturday flanking NaVorro Bowman in the nickel defense, while Armstrong took reps in the base formation. For complete 49ers coverage follow us on Flipboard.

Foster had three interceptions the first four practices and more takeaways since then, although none Saturday. His rookie season now could feature a starting role in place of Smith, a former Raider and Seattle Seahawks linebacker who the 49ers signed to a huge contract (five years, $26.5 million) partly because of his familiarity with the new scheme.

Bowman is more comfortable in the scheme having practiced next to Smith for months, and now Bowman must adapt to a new wingman while the All-Pro linebacker continues his own comeback from a serious injury, last year’s Achilles tear.

“They’re both smart. They’re both athletic,” Bowman said of Foster and Armstrong. “Ray-Ray is a great cover linebacker. We all have things we can get better at, and Reuben will definitely come down hill and smack you. They’re both smart guys.”

With Garnett out at left guard, Zane Beadles not surprisingly stepped in with Saturday’s first string. Beadles started all 16 games, the first 12 at left guard before filling in at left tackle and center. That familiarity playing between Joe Staley and Daniel Kilgore makes Beadles a reasonable solution to Garnett’s void.

Garnett has lined up almost exclusively as the first-string left guard in camp. He started the final 11 games as a rookie at right guard, which is where veteran Brandon Fusco is sewing up that starting role. Jeremy Zuttah is another option on the interior, and he hasn’t done much noticeable to unseat Kilgore at center.

2. Reid learning from GM Lynch. Before Eric Reid had another encouraging practice and before he delivered hard hits like an educational one to wayward receiver Aldrick Robinson, Reid talked several minutes on the field with general manager John Lynch, who’s been sharing knowledge from his All-Pro safety days.

“I can always seem him sneaking a peak at our drills,” Reid said. “He gives me pointers almost daily. Like our San Francisco 49ers Facebook page for more 49ers news, commentary and conversation.

“He always tries to give me a nugget if he sees something, which is cool,” Reid added. “Because to have a general manager that played the game and actually knows how it feels to be out there, you can believe him what he’s talking to you. It’s cool.”

Reid didn’t intend that as a shot at former GM Trent Baalke, who was nicknamed “Coach Trent” by Reid’s fellow defensive backs a couple years ago.

Although Reid is entering the final year of his contract and no extension talks are ongoing, there literally are signs he is seen as a franchise mainstay. Reid is among seven players whose image adorns new banners above the stadium’s south concourse.

“It is encouraging,” Reid said. “They made me feel good about my position on this team. I’m confident that I’ll be here for awhile. … I just have faith when my time comes, we’ll get a deal done.”

3. Rookies Beathard and Breida shine. C.J. Beathard further legitimized his bid for the No. 2 quarterback role, and undrafted rookie running back Matt Breida impressively introduced himself to the fans.

Beathard made a couple throws to show why he’s seriously challenging Matt Barkley as Brian Hoyer’s backup. One pass was a laser to the back shoulder of rookie Kendrick Bourne on the left sideline, and Beathard later led a 30-yard pass perfectly into the hands of a diving Breida.

“It’s a good battle for us. I look at it every day,” Shanahan said of the No. 2 quarterback race. “We evaluated (Beathard) through OTAs to see if he’d be ready to run with the (second string) more in training camp, and he earned that.”

Shanahan also praised Breida, noting: “From the first day he got here, he’s attacked everything – the weight room, the film room and on the field. It’s good to see some of that pay off today for you guys.”

Breida ran for 37 touchdowns in four seasons at Georgia Southern, and he made sure to appreciate his spot Saturday. “As soon as I walked out the tunnel, I was kind of star struck,” Breida said. “I couldn’t believe I was on a NFL field playing in front of all these fans. It was an amazing experience.”

Breida’s 5-foot-11 frame is not only fast (4.38 seconds in the 40-yard dash) but shifty, elusive and able to run through arm tackles.

“I’m nowhere near where I want to be in the NFL,” Breida said. “I’ve told myself I want to play, get to the Super Bowl, make it to the Hall of Fame, so I’ve got to keep working.”

Hall of Fame? Way to aim for the stars on the same day of enshrinement ceremonies in Canton.

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— Robinson made some exceptional catches, including a diving touchdown reception against rookie Ahkello Witherspoon. Robinson, however, also tried gaining extra yards across the middle when he got walloped by Reid’s shoulder; both Reid and Shanahan mentioned that Robinson should have headed out of bounds because it was a clock-saving drill.

“It feels good to get back in the swing of it, but speaking from a team standpoint, he’s got to get out of bounds in that situation, so hopefully that helps him remember,” Reid said.

Added Shanahan: “You better go out of bounds. Once you go inside you’re totally on your own. I couldn’t totally see it from my angle, it looked like he picked up 20 more yards. He went on his own and overcame coaching right there and did a good job. But, he can’t do that too much. It’s definitely the wrong decision until he proves us it’s right.”

— Defensive backs Rashard Robinson (hamstring) and Adrian Colbert (ankle) sustained injuries. Shanahan described Robinson’s as “tightness.” Colbert’s looked more serious.

— The 49ers have Sunday off after their sixth straight practice in full pads.

— The 49ers are low on healthy inside linebackers. Brock Coyle (ribs) and Donavin Newsom (neck) did not practice, and the freshly re-signed Jayson DiManche got hurt in his debut Saturday.