5 Steelers Questions with Behind the Steel Curtain

Are Steelers fans excited or nervous or both over the prospect of Ben Roethlisberger starting on Sunday?

If anything, I'd say they're more nervous, judging by comments on the site. The stories that have gone up about return to the field are met with more "should he be playing?" questions than "does this push us into the playoffs?" I think some of that might have to do with the dramatic performance of Charlie Batch last week - if the news before Week 13 was Roethlisberger was starting, people would have been more excited. Batch threw three picks in a loss at Cleveland.

After giving up 20+ points in 3 of the first 5 games of the season, the Steelers have yet to give up 20+ points since. Has the defense gotten better or has the competition gotten worse?

You mean competition gets worse than Oakland and Tennessee?
The Raiders (34) and the Titans (26) are two of those three teams, with Denver being the third (although they scored 31 points, seven came off an interception returned for a touchdown late in the game). I'd say the defense has gotten better, but more in the sense that they had younger players learning to fit in (CB Keenan Lewis in particular) and older players either out (Troy Polamalu and James Harrison) or working themselves back into shape (Casey Hampton missed basically all of training camp after tearing an ACL in January, 2012).
The defense has improved dramatically all season, and now, with Harrison appearing to turn the corner (pun intended) on a knee injury, they're starting to get a pass rush. Coverage has been outstanding, and the run defense has improved quite a bit.

Mike Wallace's Yards Per Reception in 2012 (11.8) are way down from his career average (17.1). Is this a result of Ben missing the last few weeks, or is there something else limiting Wallace's big plays this season?

That dips into a pretty hotly divided issue among Steelers fans. There's no doubt the offense being more balanced and controlled limits the amount of 25-plus throws in the air Wallace is used to catching, but his 11.8 yards per catch stat is probably more due to a lack of ability to make tacklers miss and make plays with the ball in his hands.
What this year is showing the Steelers (and teams wanting to pursue him in free agency) is his money spot is behind the safeties. He's dangerous in the open field, but he's clearly much better suited running fly patterns than crosses or deep digs for his big plays. He doesn't make tacklers miss.
What's clear, though, is it's not an issue of the quarterback. His numbers dipped a little bit since Roethlisberger's injury, but nothing through nine weeks suggested he was even close to being the playmaker he was through the first half of last season.

Contrary to past seasons where the Steelers had 1 or 2 strong OLB pass rushers, the sack numbers this year seem to show that Pittsburgh is getting sacks from everywhere and that no one player is really dominant. What has changed in the defense?

The Steelers got caught in the middle of the dominance they once had at the OLB position and the transitioning look of their edge rushing over the team's last 29 games. Most of that is due to injury and age. DE Aaron Smith, now retired, was, when healthy, one of the best 3-4 DEs in the game. He helped set up so much edge pressure it was hard for anyone in that spot to fail to get to the QB. Along with him, James Harrison and LaMarr Woodley played five games together all of last season. They haven't played many more than that this season. Harrison missed a lot of camp and the first few games this year with a knee injury, and, like Hampton, has been playing himself back into shape. It's starting to come back, though, he has three sacks in his last three games, and Chargers fans will want to take notice of him by the second half (when he really starts coming on) of this game.
Now, they just need to get LaMarr Woodley on the field. The hamstring donated to Woodley from a Steelers fan earlier this year was expected to have an impact (he must have missed a dozen games the last two years with hammy pulls), but an ankle injury looks to keep the once formidable pass rush of he and Harrison off the field for yet another game. His back-up, Jason Worilds, now leads the team in sacks.

In addition to Roethlisberger coming off injury, I see a lot of interesting names on the Steelers injury report: Mike Adams, Ryan Clark, Troy Polamalu, Ike Taylor, and LaMarr Woodley. How many of these guys do you expect to miss the game?

Behind The Steel Curtain will soon be selling t-shirts with the slogan "Our injury report can beat your injury report." I'm only partially kidding. That wouldn't sell, would it?
But yes, many teams have a nice mix of starters and back-ups injured in a given week. A large amount of Steelers' starters have missed at least one game this year - two of their quarterbacks, five offensive linemen (six if you include preseason starter David DeCastro who went down in August), one wide receiver, maybe one co-starting wide receiver, depending on Emmanuel Sanders this weekend, both OLBs both safeties and now a cornerback.
This week is fairly optimistic, relatively speaking. Taylor definitely will not play, I wouldn't expect Woodley or Adams to play, Clark and Polamalu both will. Being down three starters is a step in the right direction, though. As Herm Edwards said, "We can build on this!"