The injury occurred during the second quarter of the 48-32 defeat.
"We're hoping for good news on it, but if not, I know he'll do his rehab and be ready sometime next year," Shanahan told reporters.
When he is ready next year is the worrisome part.
The fact that the injury occurred so late during the season is potentially devastating news for the offensive line. The recovery for such an injury is typically in the seven- to nine-month range. That would put a potential return for Tomlinson at about late July to late September, which would obviously impact his availability for at least part of the 2019 season.
"He's a huge part of what we do," Shanahan added.
Tomlinson was replaced in the game by former first-round pick Joshua Garnett.
The 49ers acquired Tomlinson via a trade with the Detroit Lions on August 31, 2017. He missed the season opener of that season but has started each game over the past two seasons since.
The 49ers signed Tomlinson to a three-year extension on June 22, keeping him with the 49ers through the 2021 season. The new deal is worth up to $18 million.
Related News
More San Francisco 49ers News
-
Initial tests show 49ers FB Kyle Juszczyk suffered a hyperextended knee
San Francisco 49ers fullback Kyle Juszczyk will undergo further testing on Monday. Still, initial tests suggest the key piece of head coach Kyle Shanahan's offense did not suffer a long-term injury. "Initial tests showed that 49ers offensive weapon Kyle [Juszczyk]... -
49ers' Kyle Shanahan assesses Mykel Williams' return from ACL injury
San Francisco 49ers defensive end Mykel Williams returned to action Sunday for the first time since suffering an ACL injury last season. He played 23 defensive snaps and eight on special teams, recording two tackles in the 49ers' 32-29 win over the Seattle Seahawks. Williams... -
49ers GM relieved Kyle Juszczyk avoided serious injury: 'That had ACL written all over it'
The San Francisco 49ers should consider themselves fortunate that fullback Kyle Juszczyk will miss only a few weeks. After watching the veteran go down on Sunday against the Denver Broncos while favoring his knee, it was easy to fear the worst. That's exactly what general... -
49ers' Mykel Williams on improvement after ACL recovery: 'You gonna see Sunday'
Second-year San Francisco 49ers defensive lineman Mykel Williams spoke to reporters ahead of Wednesday's practice, saying he's eager to return to the field. Williams is working his way back from the ACL injury that ended his 2025 rookie campaign early. The 49ers opened his...