Which wins -- great defense or great offense?

First … Super Bowl XLI will answer one of two questions that relate to these championship games.

Do defenses win championships or do quarterbacks? The Bears are the defensive specialists. Lovie Smith has built a young defense that is two years into a possible four- or five-year run in the NFC playoffs. The Colts have Peyton Manning, who has been battling Tom Brady for the label of best quarterback over the past few years.

The defensive theme has been dominant for more than two decades. The last time a team that didn't rank in the top 10 in scoring defense won a Super Bowl was 1983 (the Raiders). The Bears' scoring defense ranked third at 15.9 points a game, and Indianapolis ranked 22nd at 22.6 points a game.

The Colts' defense also suffered a blow this week as it doesn't look like starting cornerback Nick Harper will play. He has an ankle injury that kept him out of practice Wednesday and Thursday. His foot was in a boot and he's been able to do some running in practice for only about 10 minutes in the past week.

But elite quarterbacks such as Manning usually get their Super Bowls. The list is long and distinguished. John Elway had to wait until the final two years of his career to get his Super Bowl rings. Manning's wait has been longer than expected, but is it finally his time?

The result -- one way or the other -- will be historic.

And 10. The injury factor. The Colts have the only key injury in this game and it's a significant one. Harper is a 32-year-old cornerback, but he adds a fire to this defense along with experience. He's a cornerback who often ranked among the most burned in the league, but those numbers can be misleading. The Colts often have the lead so opponents have to come back through the air. Harper's ankle is so bad that his only practice time might come Friday. That leaves him with no preparation time in the two weeks coming up to the Super Bowl. Marlin Jackson or Kelvin Hayden might get the start.

9. Getting their kicks. Adam Vinatieri is the best clutch kicker of his era and now we know why. He's tough. We've seen his mental toughness in big games as he lines up and punches through Super Bowl winning kicks with ease. The Colts simply love his toughness, period. Coaches laughed the other day about his concentration and preparation. He is demanding about his protection on kicks because kickers obviously need time to make their approach. Vinatieri told the coaches and players that if a cellphone goes off in one of the special teams meetings, he'd find the player and rip his throat out. Colts players believe him. When Manning asks him what hash mark he'd want for the ball, Vinatieri says he doesn't care. All he wants is the ball to kick. For the Bears, Robbie Gould has been clutch, too. One of the reasons is he spent the 2005 training camp with Vinatieri in New England.

8. Where did the Cover 2 go? This is supposed to be the classic matchup of Cover 2 defenses, but the Bears have been using the Cover 2 less and less in recent weeks. The two-deep zone is their base defense, and it has worked just as well as some of their Cover 2 schemes. But defensive coordinator Ron Rivera has had to tinker with it because of injuries. When the Bears lost safety Mike Brown and later lost defensive tackle Tommie Harris, he started using more schemes with one safety deep and more man-to-man. Bears cornerbacks estimate they play 45 percent man now. Rivera said he did that because Brown was such a leader and such a vital part of the defense. The loss of Harris cost them pass rush. Rivera said using more man or Cover 1 allows his defense to get closer to the line of scrimmage to play the run better. It's also helped with the pass rush. But teams have been getting more passing yards on the Bears in the second half of the season.

7. Will it be a big day for Marvin Harrison? Marvin Harrison has caught 1,022 passes for 13,697 yards during his NFL career, but he's struggled in the playoffs. Believe it or not, Harrison ranks fourth on the Colts in playoffs receptions with 10 this year. He didn't catch a touchdown pass in any of those games. If this were the regular season, Manning would consider this a mini-slump and find a way to get the ball more to Harrison. Usually, Harrison responds with a 10-plus catch day. Harrison is expected to match up against tall cornerback Charles Tillman, who might have some problems with Harrison's shifty moves. Manning removed a huge cloud over his head by winning the AFC Championship Game and taking the team to the Super Bowl. Harrison must remove the stigma he can't make plays in the playoffs and that's dangerous for the Bears. He has the potential to be a Super Bowl MVP if he gets hot.

6. The Grossman factor. You must go back to Super Bowl XXXV to find a quarterback who was criticized this much. When the Ravens beat the Giants, it was said they did it despite Trent Dilfer. Rex Grossman is in only his first full season as a starter, and it's been a tough ride. Fans wanted him replaced by Brian Griese. At times, he's been hot. More times, he's been cold. The Bears are comfortable with Grossman regardless of the temperature. In the NFC Championship Game, he was terrible. The defense kept the Bears in the game and Grossman finally got going in the second half. The key for Grossman is not winning the game. He simply can't lose it. Super Bowls are so emotional and the speed of the game is so fast, turnovers usually happen in the first half. Grossman just can't make too many of them.

5. The Dallas Clark decision. Since the season-ending Achilles injury to wide receiver Brandon Stokley, the Colts moved exclusively into a two-receiver, one- or two-tight end offense. The key to that offense is what tight end Dallas Clark does from the slot. Clark led the Colts with 17 catches and 281 yards in the three playoff games. Bears defensive coordinator Rivera faces a tough decision. Does he match up the bigger Clark with a smaller cornerback, Ricky Manning Jr., or does he stay in a regular defense with Lance Briggs? It's not an easy call. The Colts almost might prefer Rivera using the nickel and going with the small but tough Manning. With the extra cornerback in the game, the Colts face better matchups when they want to run the ball because a linebacker, probably Hunter Hillenmeyer, will come out of the game. The Bears consider Briggs a coverage linebacker in the mold of Derrick Brooks of the Bucs, but it's a lot to ask for Briggs to cover Clark the entire game. Tough call.

4. Stopping the run. Thomas Jones presents a formidable challenge for a Colts defense that surrendered 173 rushing yards a game during the regular season. There can be an argument Jones might be the most dangerous running back the Colts have faced in the playoffs. While they have seen Larry Johnson, Jamal Lewis and Corey Dillon, Jones is a cutback runner who makes quick decisions. That's the most dangerous runner facing the Colts' defense. The Colts average only 253 pounds a player in their front seven. They are quick, but sometimes their quickness hurts. If the Colts' defenders get out of their gaps by arriving too quickly, Jones can make a cut and burn them for big yardage. To make matters worse, the Bears can go to a change of pace and bring in Cedric Benson to pound the Colts with his physical style.

3. The Brian Urlacher factor. There is no doubt middle linebacker Brian Urlacher is the key to the game for the Bears' defense. He makes the defensive calls and he makes most of the big plays. Many of Manning's reads come out of what he sees from Urlacher. The Bears aren't much of a blitzing team, but they have blitzed a little more of late because of the Harris injury. The Bears and Urlacher know they have to pressure him. Manning will be watching Urlacher's every move because if he does blitz, Manning will try to get the ball into the middle of the field. Just like it's been fun watching Manning play against Tedy Bruschi and Ray Lewis, the Manning-Urlacher showdown should be a classic.

2. The Joseph Addai influence. Tony Dungy did a great job developing Joseph Addai all season. He didn't rush him and waited until the playoffs to make him a starter. Addai has been everything Edgerrin James wasn't in the last two seasons. This is no knock on James. He was a great back for the Colts and he's still a decent back in Arizona. But the pounding and James' knee problems took away some of his speed. Last year, James wasn't a threat on the stretch plays that were so vital to the Colts' offense. He didn't get to the numbers with the same speed as he used to, so the Colts had to adjust their offense. The stretch play is important for Manning. The threat of the stretch draws defenders to spots in which he can kill them with play-action passes. Addai has expanded the type of running plays the Colts can use in this game, getting them back to the old James days. Now, James was better than Addai when James played in his first five years. But Addai hasn't done badly with 217 yards in three playoff games.

1. King of the possessions. Manning is a machine. There is no quarterback in the history of the league who works a game like he does. He usually manages to get 10 offensive possessions a game. He does that out of no-huddle and making calls at the line of scrimmage. In those 10 possessions, Manning usually gets three touchdown and two field goal drives. Against good defenses, he might flop the numbers and get two touchdown drives and three field goals, but he's pretty consistent. When he gets the ball, Manning is going to get points. His regular season 56.1 third-down conversion rate is incredible. If he can do that against the Bears defense, it has the makings of a 27-17 Super Bowl victory for the Colts.

John Clayton is a senior writer for ESPN.com.