The Pittsburgh Steelers might not be the only one missing a star linebacker in Monday night’s game at Candlestick. Patrick Willis’ status remains unclear after he did not practice Thursday with the 49ers.

Willis instead rehabilitated his strained right hamstring on a side field with trainers, as was the case last week.

Willis got hurt in the first quarter of a Dec. 4 shutout of St. Louis and did not play in Sunday’s 21-19 loss at Arizona. Although he’s been seen stretching his hamstring, it’s unclear if he has started running on his reported Grade II strain.

Willis isn’t the only prominent 49ers starter who did not practice. Left tackle Joe Staley has not been medically cleared after suffering a concussion in the first quarter Sunday. Staley attended Thursday morning’s walk-through session and came out to watch the afternoon practice.

As for the Steelers’ version of Linebacker Watch 2011, they waited to see if James Harrison’s one-game suspension would be upheld by the league. Among others who did not practice Thursday were quarterback Ben Roethlisberger (ankle), safety Troy Polamalu (hamstring) and center Maurkice Pouncey (ankle).

Running back Frank Gore was not listed on the 49ers’ injury report, even though coach Jim Harbaugh noted Monday that Gore is not 100 percent. Although ankle and knee injuries have hampered Gore most of the season, he has played in every game and rushed for 1,054 yards.

Tight end Delanie Walker insisted that he is not frustrated despite having no receptions over the past four games. That span started after he tallied a season-high six catches for 69 yards against the New York Giants. Walker said he is being primarily used as a blocker now that he’s improved in that facet.

Harbaugh said he has been in touch with his brother, Ravens coach John Harbaugh, but declined to reveal what insight was shared on the Steelers, the Ravens’ AFC North rivals.

The 49ers will spend an extra day practicing their red-zone offense, going from two to three days this week, Harbaugh said.

Willis, fellow linebacker NaVorro Bowman and defensive tackle Justin Smith were named to USA Football’s All-Fundamental Team. Each player will receive a $1,500 equipment grant they can donate to a youth or high school program of their choice.

The 49ers issued a fan advisory that, among other things, asked for “reducing the decibel level” at Candlestick when the 49ers are on offense. That tip likely stems from last home game’s crowd “wave” during a third-quarter sack of Alex Smith. Fans are also encouraged to commute early to the stadium and be in their seats by the 5:30 p.m. kickoff.

The 49ers forced three turnovers Sunday and increased their league-best turnover differential to plus-21, matching the franchise’s high in 1997. (Turnover-differential statistics weren’t kept before 1995.)

The 49ers have outscored their opponents by 125 points, their highest margin since 2001 (plus-127 points).