The NFL has entered the second half of the season and the excitement is building as playoff races tighten.

In Week 10, the four division leaders in the AFC -- New England (East), Baltimore (North), Houston (South) and Denver (West) -- were all victorious. But, as another example of the unpredictability of the NFL, none of the four division leaders in the NFC -- New York Giants (East), Chicago (North), Atlanta (South) and San Francisco (West) -- recorded a win.

In the NFL, anything can happen.

The Falcons, who were the 15th team since 1978 to start a season 8-0, suffered their first loss of the season at New Orleans, falling 31-27. The Saints, who started the season 0-4, have now won four of their past five and have climbed back into the postseason picture.

"When you start 0-4 and now get the opportunity to get to 5-5, a .500 record, that's a big deal," says New Orleans quarterback Drew Brees, whose team will travel to Oakland on Sunday (FOX, 4:05 PM ET) to face the Raiders. "That means we'll have won five of our last six. That would be extremely impressive. That's something we feel like we're capable of and we envision being able to do that because we know what type of team we have. I feel like our best football is yet to come."

Week 10 also featured one of the highest-scoring days in NFL history. On Sunday, November 11, the 12 games played that day combined for 614 points. That total is the second-highest ever for a single day in which 12 games were played (628, October 25, 1987).

And last week produced the NFL's first tie game since 2008 (November 16, Philadelphia vs. Cincinnati) when the St. Louis Rams and San Francisco 49ers played to a 24-24 tie.

Some of the key games this week:

Indianapolis Colts (6-3) at New England Patriots (6-3)

(Sunday, CBS, 4:25 PM ET)

For the 10th consecutive season, the Colts and Patriots will meet. This time, New England will get its first look at Indianapolis rookie quarterback ANDREW LUCK.

Luck has guided the Colts to four consecutive wins and has won six of his first nine career starts, passing for 2,631 yards and 10 touchdowns while rushing for 159 yards and five scores. Last week against Jacksonville, Luck rushed for two TDs in Indianapolis' 27-10 win. Luck's five rushing TDs are the most by a quarterback in a season in franchise history.

"This win was huge," says Luck, the No. 1 overall selection in the 2012 NFL Draft. "We wanted to keep our winning streak going. This is a good step in the right direction, but no one looks back at the fact that you were 6-3 in the middle of the season. It's what we do at the end of the season."

The next challenge for the Colts will be going on the road to New England to face the AFC East division leader. The

Patriots have won three in a row, including last week's 37-31 victory over Buffalo.

New England quarterback TOM BRADY passed for two touchdowns last week and improved to 20-2 in his career against the Bills. The Patriots' defense helped seal the victory with an interception in the end zone with 23 seconds remaining by defensive back DEVIN MC COURTY.

"No matter what happens in the game, there's nothing bigger than a turnover," says McCourty. "When the game gets toward the end, those big plays change the game."

San Diego Chargers (4-5) at Denver Broncos (6-3)

(Sunday, CBS, 4:25 PM ET)

The Broncos lead the AFC West by two games but the Chargers will look to cut that lead in half on Sunday afternoon.

San Diego quarterback PHILIP RIVERS is 5-1 in his career at Denver with a 102.5 passer rating and the Chargers are seeking their fourth consecutive win at Sports Authority Field at Mile High. Despite a 34-24 loss at Tampa Bay last week, the Chargers know they can climb right back into the division race on Sunday by beating the Broncos.

"We know next week is as close to a must-win as it gets," says San Diego safety ERIC WEDDLE. "We'll turn around and regroup."

The Broncos are streaking as the team has won four in a row. Last week, quarterback PEYTON MANNING threw for 301 yards and a touchdown in Denver's 36-14 win at Carolina. Manning's touchdown was the 420th of his career, tying Pro Football Hall of Famer DAN MARINO for the second-most in NFL history. The victory was Manning's 147th, tying Marino for third all-time.

"This team has improved and we're developing some type of chemistry," says Manning. "We still have some things that we can do better. Any time you can learn a little bit about each other, make some progress and win some games, that's a good thing. But we still need to get better, especially down this homestretch."

Baltimore Ravens (7-2) at Pittsburgh Steelers (6-3)

(Sunday, NBC, 8:20 PM ET)

AFC North rivals Baltimore and Pittsburgh will meet at Heinz Field on Sunday night. The Ravens lead the division with a 7-2 mark but the Steelers are just one game behind at 6-3.

Baltimore got a complete team effort in Week 10 as the club scored a franchise-record 55 points in a 55-20 win over Oakland. Quarterback JOE FLACCO passed for 341 yards with three touchdowns and ran for a score, JACOBY JONES returned a kickoff 105 yards for a touchdown and punter SAM KOCH ran for a TD on a fake field goal.

"Obviously, we had success," says Flacco. "We ran the game plan and it worked well. We stuck with it. We scored points early and continued to score."

The Steelers improved to 6-3 with a 16-13 overtime victory over Kansas City on Monday Night Football, Pittsburgh's 15th consecutive home win on Monday. Linebacker LAWRENCE TIMMONS set up the game-winning field goal with an interception in overtime.

"We just stayed positive," says Timmons. "It's easy to get down, but we are not like that. We stand up and face adversity."

In the win, the Steelers had more passing yards than their opponent for the 16th consecutive home game, tied for the longest streak in NFL history (2000-01 St. Louis Rams).

Chicago Bears (7-2) at San Francisco 49ers (6-2-1)

(Monday, ESPN, 8:30 PM ET)

Two of the NFL's top defenses will meet on Monday night when the Bears visit the 49ers in a matchup between division leaders. San Francisco leads the NFL allowing 127 points (14.1 per game) and Chicago ranks second with 133 points allowed (14.8 per game).

The 49ers rank in the top three in the NFC in all three defensive yardage categories: total yards per game (292.1, first), passing yards per game (196.8, third) and rushing yards per game (95.3, third).

The Bears, who rank second in the NFC in rushing defense (92.3) and third in total defense (307.3), lead the NFL with 30 takeaways, 19 interceptions and seven interception-return touchdowns.

"We're 7-2," said Chicago head coach LOVIE SMITH after the team's 13-6 loss to Houston. "We're going to get ready for San Francisco. We have an extra day to get ready for them. There's a lot of football left to go."

The 49ers tied St. Louis in Week 10 and look to get a win on Monday.

"It prepared us," said San Francisco tight end VERNON DAVIS after the tie versus the Rams. "Chicago's a good team. They have a lot of talent. I know that we'll be ready."

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