SANTA CLARA -- While 49ers quarterback Alex Smith practiced a second consecutive day in limited fashion, Chicago counterpart Jay Cutler was a no-show Thursday as the Bears began practicing for Monday night's visit to the 49ers.

Both Smith and Cutler left their respective games Sunday with second-quarter concussions.

Smith again wore a black, no-contact jersey at practice, where coach Jim Harbaugh was noticeably absent because of an irregular heartbeat that required a minor procedure at Stanford Hospital.

Although Smith looks on track to make his 29th consecutive start, Cutler's absence Thursday could signify the likelihood he sits out from his concussion, as he did one game last season.

Bears coach Lovie Smith told the Chicago Tribune that Cutler still could start Monday night's NFC showdown even if he fails to practice this week. The Bears will travel Sunday to the Bay Area.

  • Running back Brandon Jacobs, who's yet to play this season, clarified that he was not talking about his football career when he tweeted Thursday: "Never work in a place where you hate your boss so much, you should always be happy at work. #YouLiveAndYouLearn."

    Jacobs noted -- on Twitter and to reporters -- that he has other business endeavors outside of football. He also noted that his work-related tweet came in response to his brother getting laid off at work.

  • Brandon Marshall is on pace for a career-high 1,607 receiving yards, and his average of 100.4 yards per game would be the highest in Bears history. "He's a deep threat with strong hands and a big body," 49ers safety Dashon Goldson said. "Our corners have their work cut out for them, and all of us in the secondary do."

    Practice-squad receiver Ricardo Lockette played the role of Marshall against the 49ers defense and made a one-handed, backpedaling catch against cornerback Carlos Rogers.

  • Who has the better linebacker tandem, the 49ers with Patrick Willis and NaVorro Bowman or the Bears with Brian Urlacher and Lance Briggs? "Those (49ers) 'backers are great 'backers," Briggs, a Sacramento native, said on a conference call. "I've watched them on film. Patrick, I've been to a Pro Bowl with him. And NaVorro Bowman, he's on his way. But the way I look at it is: Over here, we have 15 Pro Bowls between the two of us. And probably about eight All-Pros. We'll let that decide for itself."

    Willis is vying for his sixth Pro Bowl in six years; Bowman hasn't made the Pro Bowl but was first-team AP All-Pro with Willis last season.

  • Cornerback Chris Culliver wore a noncontact jersey and was limited at practice because of a shoulder injury. Culliver, the 49ers' No. 3 cornerback, has produced two interceptions to share team-high honors with Goldson.

  • A few new names appeared on the 49ers' first injury report since Sunday's 24-24 tie with the St. Louis Rams, those being: Goldson (ribs), center Jonathan Goodwin (ankle), guard Mike Iupati (hamstring) and running back Anthony Dixon (hamstring).

    Also listed on the 49ers' list: running back Frank Gore (ribs, wrist), Willis (hamstring), wide receiver Mario Manningham (shoulder), fullback/defensive tackle Will Tukuafu (wrist) and linebacker Tavares Gooden (elbow, quadriceps).

  • The Bears listed only five players on their injury report, three of whom did not practice: Cutler (concussion), defensive end Shea McClellin (concussion) and defensive tackle Matt Toeaina (calf). Rookie wide receiver Alshon Jeffery (hand) was limited while defensive tackle Henry Melton (back) was not.

  • Wide receiver Randy Moss has 18 touchdown receptions in 19 "Monday Night Football" games, including one on Oct. 20 at Arizona.

  • If the 49ers win, they'll tie the Cowboys for the most wins on "Monday Night Football" with 43.

    For more on the 49ers, see Cam Inman's Hot Read blog at blogs.mercurynews.com/49ers. Follow him at twitter.com/CamInman.