49ers lose Mario Manningham, Vernon Davis: NFL Week 16 injury updates

Mario Manningham posted his lowest yardage and touchdown totals since 2008 this season. (John Froschauer/AP)

The San Francisco 49ers took the worst of Sunday's injuries, with two key members of their offense leaving with potentially serious ailments. One of those hurt was Vernon Davis, who was the last of several tight ends shaken up during Week 16 action.

What do Sunday's key injuries mean for the battered players and their teams heading into the season's final week? SI.com injury expert Will Carroll provides his prognoses:

• Mario Manningham, WR, 49ers (knee): Manningham was in serious pain after taking a low hit -- so much, actually, that he fumbled the football so he could grab his knee. He was helped off the field and carted to the locker room.

Carroll: Ok, that looked ugly. But looks can sometimes be deceiving. Earlier Sunday, the oft-injured Beanie Wells came out of his end zone, jump-stopped and his knee buckled. Even with a brace, it just collapsed. He was in enough pain that he dropped the ball, allowing an easy TD recovery, but he was out there a couple series later. Manningham can only hope to be so lucky -- he buckled in a similar way, but had no brace there to take the load. He'll head for scans, but his loss would be a big one for the playoff-bound Niners.

Who takes his spot?: Rookie A.J. Jenkins, a healthy scratch Sunday, might be back in the lineup next week.

• Vernon Davis, TE, 49ers (head): Davis took such a violent hit from Kam Chancellor that he suffered a concussion, even though Chancellor did not make contact with Davis' head.

Carroll: This gives me a chance to say this one last time: When treated properly, concussions are almost always something that players recover from. The problem is that we can only say "serious" or "mild" in retrospect, that "treated properly" can be anything from a couple days to a couple years depending on symptoms, and that we've barely scratched the surface when it comes to long-term effects or the problem of repeated subconcussive impacts. We'll see how Davis does sooner than the NFL will figure all this out, but the number of concussions is up. That's a bad sign for thinking that fines and penalties would reduce things.

Who takes his spot?: Delanie Walker caught a TD pass later, though Garrett Celek may take on an increased role if Davis misses time.

• Matt Forte, RB, Bears (ankle): Forte reinjured his right ankle, which has troubled him throughout 2012. He missed most of the second half Sunday and likely will be questionable for Week 17.

Carroll: Simple can be good or bad. Matt Forte has a simple ankle sprain -- the "low" or "basketball" sprain that we're used to seeing. He left the game in a walking boot, and there are questions about how serious the sprain is. A Grade II could keep him out longer than he has season left and it raises the issue of whether Forte wears down over the course of a year. He's in fine physical condition and he wasn't overworked, but at some point this becomes a "tissue issue" -- perhaps Forte can't hold up no matter what he or the Bears do. Listen for the grade of sprain, and then for him to do cutting to the opposite side of the injury.

Who takes his spot?: Chicago's already down Michael Bush for the season, so Kahlil Bell and Armando Allen may split carries at Detroit next Sunday.

• Scott Chandler, TE, Bills (knee): Chandler appeared to suffer a serious knee injury after making a 25-yard catch early. He did not return.

Carroll: The Bills had no reports, but Chan Gailey's "doesn't look good" comment usually translates into "we think it's the ACL." Chandler will head for scans and a possible surgery. Chandler doesn't have the athleticism of an Adrian Peterson, but his size is his skill. That said, an ACL reconstruction would likely have him on the shelf for at least the start of next season.

Who takes his spot?: Lee Smith moved up to the No. 1 tight end role Sunday. If Chandler is out for Week 17, the Bills may have to make a roster move.

• Randall Cobb, WR, Packers (ankle): Cobb stayed down after a third-quarter punt return and did not return.

Carroll: Randall Cobb sprained his ankle and did not return Sunday, but by the time the trainers had his tape off, the Packers were on their fifth TD. Some sources said Cobb could have returned if need be, and on Monday coach Mike McCarthy said Cobb will again serve as Green Bay's punt returner if Cobb is healthy enough to go in Week 17. That doesn't sound like a coach who's too concerned about the extent of this injury or its impact on the game plan.

Who takes his spot?: Jeremy Ross took over as Green Bay's punt returner, though it sounds like Ross will be back on the bench if Cobb suits up. Donald Driver, who saw just one target Sunday, could be in line for more work next week if Cobb's snaps are at all limited.

• Brooks Reed, LB, Texans (groin): Reed pulled himself from the lineup Sunday, later saying he did not want to hurt the team by playing at less than full speed.

Carroll: Brooks Reed aggravated his groin strain in Sunday's loss. With the Texans locked into the playoffs but needing a win to hold seed, they face some very difficult choices heading into a very emotional game with the Colts. Normally, the Texans would rest players once they had a comfortable lead, but with Chuck Pagano's return, the Texans know they're heading into a game where "normal" isn't going to be in play. Expect the Texans to be very conservative with any banged-up players, including Reed and Arian Foster, whose irregular heartbeat was said to be minor.

Who takes his spot?: Whitney Mercilus took Reed's spot full-time when Reed was out earlier with the same injury.

• Brandon Weeden, QB, Browns (shoulder): Weeden injured his throwing shoulder on a hit from Von Miller in the third quarter.

Carroll: The Browns can go with Colt McCoy next week if there's any question and figure to be a bit conservative with their not-so-young QB heading into an offseason that will put his future up in the air. It will be that way for next week if there's any significant damage or even a slight injury.

Who takes his spot?: McCoy finished up Sunday and would be the No. 1 at Pittsburgh next week, if Weeden has to sit.

• Heath Miller, TE, Steelers (knee): Miller was rolled up on while blocking during a run play and tore his ACL and MCL. He also has a possible PCL tear.

Carroll: The Steelers' season is over, and so is Miller's. A knee injury of this severity will require surgery and extended rehab, so there's no guarantee Miller will be ready to start the 2013 season on time. After producing a Pro-Bowl-caliber 2012 campaign, Miller faces an uphill battle heading into next year. (UPDATE: Bad news. The MRI showed that Miller also tore his ACL. With all three ligaments torn, he'll be pushing it for the start of next season. Just a devastating injury on top of such a tough year for the Steelers.)

Who takes his spot?: Leonard Pope and David Paulson are the Steelers' remaining tight end options for an essentially meaningless Week 17 game vs. Cleveland.

• Anquan Boldin, WR, Ravens (shoulder): Boldin came down hard after diving for a catch in the third quarter.

Carroll: With the Ravens locked into the playoffs, they won't risk Anquan Boldin and may be very light on starters next week all around. Boldin's shoulder injury is said to be "mid-grade" according to a couple reports, which is oddly specific. It indicates a sprain, likely an AC sprain, and not having the bye means they'll definitely be holding Boldin out unless mid-grade is an exaggeration.

Who takes his spot?: