SANTA CLARA, Calif. – While the San Francisco 49ers will be without left tackle Trent Williams for the fourth straight game on Thursday night, there is at least a chance that three other key players will be available.

The Niners officially ruled out Williams (left ankle), safety Malik Mustapha (chest, shoulder) and guard Ben Bartch (high ankle sprain) Wednesday afternoon, but have ruled out defensive end Nick Bosa (left hip, oblique), running back Isaac Guerendo (foot) and linebacker Dre Greenlaw (Achilles) is listed as questionable.

Bosa has missed the last three games after suffering an injury to his left side in a loss to the Seattle Seahawks on November 17th. While the 49ers have done nothing but a walk-through in practice over the past three days due to short turnarounds, Bosa was listed as a limited participant in Wednesday’s meeting. It is the first time he has taken part since November 15th.

Greenlaw has yet to play a snap this season after tearing his left Achilles tendon in Super Bowl LVIII. San Francisco opened Greenlaw’s 21-day practice window on Nov. 27 with an eye toward his return this week.

On Monday, Niners coach Kyle Shanahan said Greenlaw had “a chance” of being activated for the game against the Los Angeles Rams, depending on how the week went.

“We’ll see,” Shanahan said. “I haven’t spoken to him yet, so we’ll see when he gets here tomorrow, how he feels, how training goes on Tuesday and Wednesday and then make our decision.”

According to the injury report, Greenlaw had little trouble this week. He has been a limited participant at every practice he has attended in recent weeks, but was listed as a full participant for the first time during Wednesday’s walkthrough.

If the 49ers activate Greenlaw, they would have to make a move before Thursday night’s game. The obvious option would be to place Bartch on injured reserve to create a spot for Greenlaw on the 53-man roster.

As for Guerendo, he didn’t do anything on Monday and Tuesday, but was upgraded to limited in Wednesday’s walk-through. After injuring his foot against the Chicago Bears last week, Guerendo insisted he could play against the Rams.

“Everything is fine,” Guerendo said Sunday. “They’re just being careful. We have a quick turnaround this week, so let’s just make sure we’re ready to go.”

The 49ers are already without running back Christian McCaffrey (right PCL), Elijah Mitchell (hamstring) and Jordan Mason (high ankle sprain). If Guerendo is unable to play or is limited, Patrick Taylor Jr. would be next in line to work out of the backcourt, with practice player Ke’Shawn Vaughn and recently added Israel Abanikanda also available as options.

Mustapha’s absence comes as a bit of a surprise after he was listed as limited availability for Monday and Tuesday. But he did not attend Wednesday and was expelled. Ji’Ayir Brown and Tashaun Gipson Sr. are San Francisco’s top options to start alongside Talanoa Hufanga in place of Mustapha.