Week 12 NFL injuries: Troy Polamalu among key players to fall

Troy Polamalu suffered what is believed to be another concussion making this tackle agianst the Chiefs Sunday night, and could miss significant time. (AP)

It's hard enough to replace a starter this late in the season, when every game carries so much importance. But what does a team do when its second option at a position also falls? That's the predicament now facing the Texans, who lost new starter Matt Leinart Sunday with Matt Schaub already on the shelf. The Lions might have the same issue, with running back Kevin Smith -- the team's latest fill-in for Jahvid Best -- exiting their Thanksgiving Day game.

The injuries in Week 12 were not as numerous as some other weeks, but the players that did drop are critical to their teams' hopes. Helping break down the impact this week's injuries will have is SI.com's injury expert Will Carroll.

• Troy Polamalu, S, Steelers (head): The Steelers lost Polamalu early Sunday night after he went low to make a tackle, then came up wobbly. Polamalu was put through a series of concussion tests on the sideline and did not return.

Carroll:  The Steelers are playing their normal "symptoms" game, rather than just saying that hitting his head against a big knee gave Polamalu his second (at least) concussion of the season. Polamalu's style of play makes him good, but also leaves him susceptible to these kinds of injuries. Polamalu was wearing one of the new Simpson-brand helmets earlier this season, but it's not clear whether he was wearing it Sunday night. If he was, it would be the first concussion for the Simpson.

Who takes Polamalu’s spot?: Ryan Mundy stepped into the lineup, and Pittsburgh held up well against the Chiefs -- in part because of Tyler Palko's presence at quarterback. But the Steelers have seen first-hand how damaging a Polamalu injury can be to their defense.

• Matt Leinart, QB, Texans (shoulder): The Leinart era in Houston lasted less than one half. As he let go of an incomplete pass against Jacksonville, Leinart was wrapped up and driven to the turf, landing hard on his shoulder. His season may be over.

Carroll: Tough break -- literally -- for Leinart. They haven't come up with shoulder pads yet that allow a QB freedom of movement and protect him when driven into the turf with a 300-lb. man on top of him. Leinart had a similar injury in Arizona and recovered well, as did Dallas' Tony Romo.

Who takes Leinart’s spot?: The Texans turned to rookie T.J. Yates Sunday, and he finished off a win over Jacksonville. It looks like his job going forward, too, though there were rumors Monday that the Dolphins would release Sage Rosenfels so he could sign in Houston.

• Kevin Smith, RB, Lions (ankle): Smith had to be carted off in Detroit's Thanksgiving Day loss to Green Bay after injuring his ankle. He had 36 yards on seven carries prior to suffering his injury.

Carroll: Smith had a freak high ankle sprain. It was a non-contact injury that the Lions can blame on their turf. Smith turned to his right and his foot stayed in place, taxing the ligament. It's not considered serious, but as we saw with Adrian Peterson, even a mild high-ankle sprain is one that can keep a running back out a while. Smith is quick and shifty, so it's going to hurt him even more.

Who takes Best’s spot?: Detroit would be back in the unenviable spot it was in prior to signing Smith -- which is with Maurice Morris and Keiland Williams pressed into duty at running back.

• Sidney Rice, WR, Seahawks (head): Rice, who also missed Weeks 1 and 2 this season, hurt himself Sunday when he landed hard on the turf while extending to make a catch. He walked gingerly to the sideline, then was helped to the locker room.

Carroll: Rice dove, caught the ball, and then had his helmet hit awkwardly against the ground. His arms pushed out in the "fencer's response" you often see with concussions, a clear sign of unconsciousness and the severity of the concussion. He'll be checked under the NFL protocol, but he was responsive after the game.

Who takes Rice’s spot?: Doug Baldwin caught five passes to lead Seattle vs. the Redskins. He, Ben Obamanu and Golden Tate all could see increased looks if Rice is out for an extended period of time.

• Brent Grimes, CB, Falcons (knee): Grimes appeared to suffer a non-contact knee injury in the first quarter of Atlanta's win over Minnesota. He did not return to the game.

Carroll: Brent Grimes came back from a knee injury ... to get another one. At this stage it's not clear whether Grimes re-injured the knee that he originally hurt back in Week 9 or whether it's a new injury, but Grimes is a key part of the Falcons secondary.

Who takes Grimes’ spot?: Chris Owens slid into the Atlanta secondary after Grimes left, but Grimes is an undervalued member of the Falcons' defense. He had 11 interceptions over the past two seasons and has 12 pass breakups this year.

• Montario Hardesty, RB, Browns (calf): Hardesty was expected to join Peyton Hillis in a return to Cleveland's backfield Sunday, but his previously injured calf tightened up during warmups.

Carroll: Someone's going to have to at least ask why the Browns keep re-injuring themselves. Hillis had a huge setback with his hamstring, coming back only Sunday. Hardesty re-injured his calf during warmups and like Hillis, there are reports that this has set Hardesty all the way back.

Who takes Hardesty's’ spot?: Hillis carried the bulk of the load Sunday and would continue to do so, as long as he stays healthy. Chris Ogbonnaya is Cleveland's second option for the moment.

• Brian Price, DT, Bucaneers (ankle): Price was carted off just before halftime of Tampa Bay's win over Tennessee and had a walking boot on Monday.

Carroll: There's few details yet on Brian Price and his ankle/leg injuries, but its clear he's going to miss extended time. The Bucs have gone through D-line bodies, necessitating the move for Albert Haynesworth. Price left Sunday's game on crutches among reports that he had a fracture. We'll have to wait and see if the Bucs will be looking for another DL again.

Who takes Price’s spot?