SANTA CLARA — When the San Francisco 49ers opened training camp on Wednesday there was much more intrigue about the players not on the field than the ones taking part in practice.

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Aiyuk Watches Practice in Street Clothes

All-Pro left tackle Trent Williams is holding out as he seeks a more lucrative contract, and star receiver Brandon Aiyuk is conducting a “hold in” as he waits for a contract extension.

Aiyuk watched the first few minutes of practice in street clothes before walking off the field early in the session. He is currently under the fifth-year option worth about $14.1 million this season but is looking to become the latest receiver to cash in on a big multi-year deal.

San Francisco coach Kyle Shanahan said Aiyuk reported having a sore back and neck but characterized the absence as a “hold in.”

“It’s what we expected and I understand the situation fully,” Shanahan said.

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Williams’ Absence a Bigger Immediate Issue

Williams’ decision to skip the start of camp was a bigger immediate issue, with Shanahan describing it as “contract related.”

General manager John Lynch has been speaking this offseason with Williams’ representatives about a new deal to replace the final three non-guaranteed years of a six-year, $138.1 million contract signed in 2021.

Williams is owed a base salary of about $20.1 million this season with an additional $750,000 in per-game roster bonuses. Williams is subject to a mandatory fine of $50,000 for each day of training camp he misses.

“It was something I knew could be a possibility,” Shanahan said. “I was hoping he would be here, but I knew it could be a possibility. I feel pretty confident that it will all work out in the long run and he’ll be here and we’ll get on the same page with everything. But it’s just one day of practice and I think Trent will be all right missing a few practices.”

Williams has been the best left tackle in the NFL since joining the Niners in 2020. He has been a first-team All-Pro the past three seasons, and the 36-year-old has made 11 Pro Bowls.

Williams is by far the best player on an offensive line that lacks any other top performers, making his absence a major concern.

“That’s one of our best players, one of our leaders,” All-Pro linebacker Fred Warner said. “But we understand the business side of it. This isn’t our first rodeo. It’s a curse and a blessing to have so many great players as part of our team. We’ll get it figured out.”

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49ers Have Rewarded Homegrown Stars

The Niners have done a good job rewarding their homegrown stars, handing out megadeals the past four offseasons to George Kittle, Warner, Deebo Samuel and Nick Bosa.

Samuel missed a handful of practices in 2022 as a “hold in” and Bosa held out until a few days before the season opener last season. Both players said the long contract disputes weighed on them and impacted their performance during those seasons.

Aiyuk was a key part of San Francisco’s offense last season as he developed a great connection with quarterback Brock Purdy. Aiyuk had 75 catches and a career-high 1,375 yards last season with seven touchdowns as he earned second-team All-Pro honors.

Eight receivers before Aiyuk had signed contracts worth at least $70 million already this offseason, with Justin Jefferson’s four-year, $140 million extension with Minnesota setting the top of the market.

NOTES: Rookie RB Isaac Guerendo left practice early with a right hamstring injury. … All-Pro RB Christian McCaffrey didn’t take part in team drills as the club eases him into camp. … Rookie S Malik Mustapha made the defensive play of the day when he ranged from his deep safety spot to intercept a deep pass from Joshua Dobbs to Danny Gray.