(AP Photo/Charlie Riedel)

Being undefeated is extremely rare in the NFL.

The Miami Dolphins did it in 1972. Tom Brady and the New England Patriots almost pulled it off in 2007. As each NFL season progresses, the undefeated teams get fewer and fewer until normally none remain.

Entering Week 4 in the NFL, there were seven undefeated teams. Exiting Week 4 only five teams remain undefeated — Kansas City Chiefs, New England Patriots, Denver Broncos, New Orleans Saints and Seattle Seahawks. From nail-biting finishes to 32-point blowouts, this past week was full of big stories.

Here are the best and worst from the week.

For additional NFL coverage, you can follow Mitch Kunzler on Twitter: @MitchKunzler.

(AP Photo/Charlie Riedel)

Best: Alex Smith, Andy Reid, Chiefs continue to work their magic

Coming off the worst NFL win-loss record of the 2012 season, the Kansas City Chiefs have improved to 4-0, doubling their wins of last season. In Week 4, the Chiefs faced off against the New York Giants, and two-time Super Bowl MVP Eli Manning. The Chiefs' defense held Manning to just one passing touchdown, whereas Kansas City quarterback Alex Smith threw for 288 yards and three touchdowns. The Chiefs dominated the Giants, 31-7.

The Chiefs will look to extend their perfect season on Sunday against the Tennessee Titans.

(AP Photo/Gary Wiepert)

Worst: Joe Flacco throws five interceptions

Baltimore Ravens' quarterback Joe Flacco didn't look like the defending Super Bowl MVP on Sunday against the Buffalo Bills. In fact, he looked completely the opposite. Because the Ravens couldn't get the run game going, Flacco suffered in the passing game. Although he threw for two touchdowns, Flacco also threw five interceptions, which ended up being the deciding factor in the final score. When the clock reached zero, the Bills had topped the Ravens 23-20.

Flacco's interceptions are a huge issue for the Ravens this season, and that is something he is well aware of.

"A lot of that falls on me today and just throwing the ball to the wrong team," Flacco told ESPN. "If we don't do that, then this game probably looks a little different."

Flacco will look to keep his interceptions to a minimum on Sunday when the Ravens head to Miami to face the Dolphins.

(AP Photo/John Bazemore)

Best: Tom Brady, Patriots remain unbeaten despite injuries

Because all-star tight end Rob Gronkowski and receiver Danny Amendola remain injured, many thought that the New England Patriots would return from Atlanta Sunday with their first loss of the season. Tom Brady thought the opposite, however. Brady made is young receivers look like veterans in throwing for 316 yards and two touchdowns against the Falcons.

The Patriots scored 17 points in the fourth quarter and survived a late rally by the Falcons to win, 30-23. With Sunday's win, the Patriots improve to 4-0. The last time New England went 4-0 it went on to go undefeated in the regular season.

(AP Photo/Matt Dunham)

Worst: The Steelers can't rally, drop top 0-4

The Pittsburgh Steelers are off to their worst start in years. No matter what they do, there is just no consistency. The Steelers suited up in London Sunday in a match-up that pitted them up against defending MVP Adrian Peterson and the Minnesota Vikings. Both teams were winless heading into the game.

Despite a close finish, the Steelers couldn't contain Peterson, who rushed for 140 yards and two touchdowns in leading the Vikings to a 34-27. The Steelers to 0-4 for the first time since 1968. For Steelers' quarterback Ben Roethlisberger, it is a painful experience.

"We are in unchartered territories and the water is dangerous right now, so we have to stick together and get out of it," Roethlisberger told CBSSports. "Right now, you could say we're the worst team in the league. That hurts."

For one of the most storied franchises in the NFL, these winless circumstances are making Pittsburgh desperate. The Steelers have a chance for redemption Sunday against the New York Jets.

(AP Photo/Jack Dempsey)

Best: Peyton Manning scorches Eagles defense, Broncos special teams come up big

Normally when you have one of the best quarterbacks to ever play the game matched up against the worst total defense in the NFL, the quarterback is going to come up huge. For Denver Broncos' quarterback Peyton Manning, it was no different. Manning threw for 327 yards and four touchdowns on the Philadelphia Eagles' crumbling defense, which ended Manning's September with 16 touchdown passes — the most in NFL history after four weeks. He has yet to throw an interception.

The Broncos special teams also came up big against Philadelphia. Trindon Holliday returned a kickoff 105 yards for a touchdown and Steven Johnson blocked a punt that he scooped up for a touchdown.

If the Denver offense, defense, and special teams can continue to play this flawless, the Broncos might not lose this season.

(AP Photo/Wade Payne)

Worst: Titans' Jake Locker out 4-8 weeks

Tennessee Titans' quarterback Jake Locker injured his hip during a 38-13 win over the New York Jets Sunday, which doesn't bode well for the Titans. According to ESPN, it is believed that Locker will miss anywhere from 4-8 weeks with this injury.

Locker, who has thrown for 721 yards, six touchdowns, and zero interceptions this season, seemed to be the spark the Titans needed to make a statement in 2013. While Ryan Fitzpatrick is a suitable replacement, he lacks Locker's athleticism to make plays with his feet. The sooner Locker returns, the better for Tennessee.

(AP Photo/Bill Feig)

Best: Brees, Saints win the undefeated match-up

Monday Night Football was an anticipated one in Week 4 with the unbeaten New Orleans Saints facing off against the unbeaten Miami Dolphins. This particular match-up got a lot of attention this past week.

Drew Brees reminded everyone why he is an elite quarterback in the league. He passed for 413 yards and four touchdowns with zero interceptions. No matter what defensive look the Dolphins threw his way, Brees easily executed in leading the Saints to a 38-17 win.

With Monday's win, the Saints improve to 4-0, and head to Chicago to play the Bears Sunday. The Dolphins add the first loss to their record, but look to get back on track against the Ravens Sunday.

(AP Photo/The Florida Times-Union, Bruce Lipsky)

Worst: Jaguars look lost

The Jacksonville Jaguars are in a world of trouble. Their star running back, Maurice Jones-Drew, is playing with a high ankle sprain, but he just can't seem to make any difference. Jones-Drew carried the ball 13 times for 23 yards Sunday in a 37-3 loss to the Indianapolis Colts.

Jaguars' quarterback Blaine Gabbert threw three interceptions and no touchdowns, which puts his season stats at zero touchdowns, five interceptions. With free-agent quarterbacks like Tim Tebow and Vince Young available, it is very odd that the Jaguars haven't shown any interest in getting another quarterback.

If Jacksonville doesn't make any moves, expect them to drop to 0-5 after Sunday's game against the St Louis Rams.

(AP Photo/David Richard)

Best: Browns have resurrected their season

After the Cleveland Browns traded away second-year star running back, Trent Richardson, most thought that they were tanking their season. They had an 0-2 record, and giving away their best player and it seem like that they had given up and accepted that they didn't have a chance.

But that was before Brandon Weeden had a thumb injury, which caused fifth-year quarterback Brian Hoyer to become the Browns' starter. Since then, the Browns have won both of their games, including Sunday against the Bengals. Hoyer threw for 269 yards and two touchdowns in the Browns' 17-6 win over Cincinnati.

The Browns have all sorts of momentum right now. Even though Weeden is cleared to play, don't expect him to replace Hoyer, if Cleveland keeps winning.

(AP Photo/David J. Phillip)

Worst: Texans blow late game lead, Richard Sherman capitalizes

The Houston Texans were leading the Seattle Seahawks 20-13 with a little under three minutes left in the game. That is when Seattle cornerback Richard Sherman jumped in front of Houston's tight end Owen Daniels to intercept a pass and take it 58 yards for a touchdown. It was a dangerous play and Sherman knew the risks.

"It's a high-risk, high-reward play," Sherman told ESPN. "You have to jump in, and you might get beat over the top for a 20- or 30-yard gain, if he gets the ball down there. But if you make the play, you might get a pick-6 and change the game for your team."

And change the game for his team is exactly what he did. The interception return tied the game, and in overtime, the Seahawks kicked a field-goal to win, 23-20.

The Texans lead the NFL in total defense and it was tough to see the offense give away the game in the end. For defensive end JJ Watt, it was extremely upsetting to see a game like this slip away.

"We were dominating the whole first half ... and the second half we just didn't finish the game," he said. "It's very, very frustrating."

The Texans can't mourn their loss for long, however. They have to prepare for another NFC powerhouse, the San Francisco 49ers, who they play on Sunday.

(AP Photo/Patric Schneider)

With the first four weeks of the 2013 NFL season in the past, it is shaping up to continue to be a great year for football. With records being broken every week, and the group of undefeated teams shrinking smaller and smaller, Week 5 has great things in store.