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Posted by ESPN.com’s Bill Williamson

San Diego standout linebacker Shawne Merriman is listed as questionable to play Sunday night at Pittsburgh in a pivotal game for the Chargers.

Merriman made significant strides Friday by practicing fully. He has a groin injury and he practiced on a limited basis Thursday after practicing Wednesday. Merriman has missed significant parts of the past two games with the injury.

Meanwhile, San Diego running back LaDainian Tomlinson is listed as probable and he is expected to play at Pittsburgh. Tomlinson has practiced all week. He missed the past two games with an ankle injury.

For Pittsburgh, safety Troy Polamalu was ruled out by the Steelers. It's the third straight game he’ll miss with a knee injury. Expect San Diego to try to exploit Polamalu’s absence by getting the ball to tight end Antonio Gates often.

Posted by ESPN.com’s Bill Williamson

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Five nuggets of knowledge about Sunday’s games:

	Ezra Shaw/Getty Images
	The Raiders need defensive end Richard Seymour to break out this week against Houston.

Seymour needs to make an impact: The Oakland Raiders need a spark and the perfect player to give it is Richard Seymour. The Raiders traded a first-round pick in 2011 to New England to get Seymour because they wanted the potential hall of famer to bring the team to the next level. The defensive end looked like he’d be that player in the season opener when he had two sacks against San Diego. In the two games since, Seymour has been quiet. Yes, he’s been double teamed, but he hasn’t produced much. The only noise he made was when he pulled the hair of Denver tackle Ryan Clady. He was penalized 15 yards for it. The Raiders are slumping into Houston. They need their veteran star to bring new life.

Rivers needs to go deep: San Diego quarterback Philip Rivers is becoming one of the premier deep-ball passers in the NFL. His deep passes are a thing of beauty. They are text book. Rivers has arrived as an elite player and he does few things wrong. But he has mastered the long ball and used it to his advantage in each game this season. Expect him to fire away Sunday at Pittsburgh. The early-season MVP candidate will try to take advantage of the absence of Pittsburgh star safety Troy Polamalu and try to shred the Steelers with a deep pass or two.

Time for the Broncos to show they are for real: The Broncos are one of seven unbeaten teams in the NFL and are the early surprise. Not much was expected from Denver in the first year of the Josh McDaniels’ era. But the team has been menacing on defense and timely on offense. Still, there are skeptics. Denver has beat Cincinnati, Cleveland and Oakland. But the easy ride is over. Denver starts a 10-game stretch in which they play eight sure playoff contenders. The rough road begins Sunday at home against Dallas. If the Broncos can dispatch the Cowboys, they will start to get respect and be considered a true playoff contender. If Denver loses to the visiting Cowboys, they will be cast as a pretender.

Chiefs have to compete in second leg of NFC East tour: Chiefs coach Todd Haley was criticized after last week’s 20-point loss at Philadelphia. Haley started to run the ball more in the second half instead of passing the ball even though the Chiefs were down by more than two touchdowns. The Chiefs have to find a way to stay in the game this week against the visiting Giants. Just like against the Eagles, the Chiefs will be badly overmatched. But this team, which competed well in the first two games under Haley, has to find a way to compete as they play their second of four straight games against NFC East competition.

This is the time for Russell to shine: I spoke to KC Joyner, the Football Scientist, this week. Joyner, a number cruncher supreme, said he believes Oakland quarterback JaMarcus Russell could have a decent game against Houston. If not, Joyner surmised, Russell really may be on his way to becoming a bust. Joyner thinks Houston has one of the worst defensive backfields in the league based on his computing. Houston’s cornerbacks are allowing big plays at an alarming rate. It’s a perfect opportunity for Russell to break out. If not, Russell (who has a 39.8 passers’ rating this season) may never break out.