With the Seattle Seahawks and New England Patriots each losing their first game in week five, the number of undefeated teams left in the NFL dropped from five to three this past week. The Denver Broncos, New Orleans Saints and Kansas City Chiefs are the three teams that still haven't lost this season, and as the season progresses, that list will undoubtedly shrink.

On the flip side, the Jacksonville Jaguars, Tampa Bay Buccaneers, Pittsburgh Steelers and the New York Giants are all teams in the NFL that still haven't won a game.

Such extreme differences in the NFL win/loss records correctly reflect the way this season has gone so far: a lot of ups and a lot of downs. Here are the best and worst from week five in the NFL:

You can follow Mitch Kunzler on Twitter at @MitchKunzler.

Best: Alex Smith and the Chiefs do it again

In week five of the 2012 NFL season, the Kansas City Chiefs were 1-4, and well on their way to finishing with the worst record in the league. That was before Andy Reid was named as the head coach and Alex Smith became the starting quarterback.

Smith led the Chiefs to battle against the Tennessee Titans on Sunday, a team Chiefs' coach Reid had never won a game against. Smith put together a fourth-quarter drive that gave the Chiefs the lead. The Kansas City defense then went on to snag two interceptions to seal the victory, winning 26-17.

With Sunday's win, the Chiefs move to 5-0, joining the Denver Broncos and New Orleans Saints as the only undefeated teams left in the NFL.

Worst: Michael Vick suffers a hamstring injury

The Philadelphia Eagles and the New York Giants met for their rivalry game on Sunday, one that wouldn't bode well for the Giants, as they lost 36-21. The Giants had trouble stopping Michael Vick's running game, as he had nearly 80 yards on the ground in the first half. As the half neared an end however, Vick injured his hamstring. Eagles' back-up quarterback Nick Foles finished the game for the Eagles, keeping the lead and securing the victory.

Vick's injury is anticipated to keep him out this week against Tampa Bay. Foles looked solid from a passing standpoint, but Philadelphia's run game suffered tremendously without Vick. For a fast-paced, read option style offense like the Eagles have, Foles doesn't really produce any threat on the ground, leaving the running backs to be easily targeted every play.

While the win on Sunday gives the Eagles a share of their division lead, they will need a healthy Michael Vick to give them a chance at maintaining the lead.

Best: Andrew Luck, Colts prove that Seattle can be beat

One of the most intriguing matchups of week five was the Indianapolis Colts versus the Seattle Seahawks, a game that pitted the undefeated Seahawks against young quarterback Andrew Luck. Luck has shown promise since he entered the NFL, and is on his way to becoming an elite quarterback in the league. The Seahawks' defense is arguably the best in football, and a battle against the young Colts' quarterback was anticipated all last week.

Coming into the game, Luck had more fourth quarter comeback victories (with eight) than any other quarterback since he entered the league. He would add to that number on Sunday, as his late-game heroics led the Colts to a 34-28 upset victory over Seattle.

Luck was extremely collected throughout the game, throwing for 229 yards and two touchdowns. While many have doubted Luck's ability, it is clear that the Colts have a solid franchise quarterback for years to come.

Worst: Tom Brady's streak ends

Before Sunday's game against the Cincinnati Bengals, New England Patriots' quarterback Tom Brady had thrown for at least one touchdown in 52 consecutive games. That streak ended as the Bengals' defense pressured Brady and mauled New England's young receivers, leading to the Patriots losing the game 13-6. Brady's lack of consistent receivers has been a problem all season long, and up until the matchup with Cincinnati, Brady had managed to lead the Patriots to an undefeated season in spite of them. It couldn't last, as their weaknesses finally got the best of them in week five.

With tight end Rob Gronkowski set to return this weekend, receiver Danny Amendola looking healthier, and former BYU receiver Austin Collie now signed, the Patriots receivers look as though they will be much improved in week six.

Best: Geno Smith leads the Jets to their third fourth-quarter comeback of the year

When the word "clutch" is mentioned in the NFL, the faces that normally come to mind are that of Eli Manning, Tom Brady or Andrew Luck. New York Jets' rookie quarterback Geno Smith is beginning to make his case for being mentioned among those clutch quarterbacks.

Smith led the Jets on yet another fourth-quarter comeback victory on "Monday Night Football" against the Atlanta Falcons. Smith and the Jets' offense got the ball with 1:54 remaining, trailing the Falcons by one point. Smith then put together a clutch drive like only a few quarterbacks in this league could, as the Jets drove the ball 55 yards down the field, which set up a field goal as time expired, giving the Jets the 30-28 victory. Smith ended with three passing touchdowns and zero interceptions.

Monday's victory was the third fourth-quarter comeback win that Geno Smith has orchestrated this year, which leads the NFL. With the composure and veteran-like leadership that Smith has demonstrated all season long, it's hard not to love this kid.

Worst: Julio Jones likely out for the season

Not only did the Atlanta Falcons lose a nail-biting game to the New York Jets, but they may have suffered a devastating loss to their offense. According to USA Today, the Falcons' best receiver, Julio Jones, has suffered a foot injury, the results of which are likely to make Jones miss the remainder of the season.

If Jones does indeed miss the remainder of the season, it will be a huge blow to the Falcons, considering that Jones has been the only real bright spot in an otherwise disappointing Falcons team. Jones is currently second in the NFL in receiving yards and first in receptions.

Best: Jimmy Graham dominates, ties NFL record

Not only did the New Orleans Saints improve to 5-0 with a win over the Chicago Bears, but they have also discovered how big of a threat that tight end Jimmy Graham can be. Graham recorded his fourth straight 100-yard receiving yards, which ties an NFL record for such a game for a tight end.

According to the NFL on ESPN, if Graham keeps up his production for the rest of the season, he is on pace for 118 catches, 1,897 yards and 19 touchdowns. Drew Brees definitely has a safety blanket at his disposal.

Worst: Eli Manning's interception woes

New York Giants quarterback Eli Manning is having an awful season. The two-time Super Bowl MVP leads the league in interceptions (with 12), and the Giants are currently 0-5. For the NFL, this comes as a shock considering how dominant the Giants have been in the past decade.

While the Giants aren't likely to bench Manning for backup quarterback Curtis Painter, the Giants definitely need to make some kind of change. This team is clearly not capable of winning football games and is in desperate need of a spark.

If the Giants don't find some way to energize themselves, then it will continue to be an extremely long season for Giants fans.

Best: Terrelle Pryor proves that he is no joke

Not many people expected the Oakland Raiders to have a good season, and sitting at 2-3, it seems that the Raiders aren't worth talking about. However, Raiders quarterback Terrelle Pryor is definitely giving Raiders fans something to smile about.

The Raiders played the San Diego Chargers late Sunday night, a game in which the Chargers were favored to win. Pryor, however, had other plans. He completed 18 of 23 passes for 221 yards, two touchdowns and zero interceptions, leading the Raiders to a 27-17 upset over San Diego.

Since the victory, the Raiders have released quarterback Matt Flynn, who was originally believed to be the starter for Oakland this season. With Flynn's release, it is clear that the Raiders are committing to Pryor as the quarterback going forward. With Pryor under center, the Raiders will always have a chance.

Worst: Tony Romo chokes again

The matchup between the Denver Broncos and the Dallas Cowboys was an epic shootout to say the least. Both defenses had trouble stopping the offenses, as Broncos quarterback Peyton Manning threw for 419 yards and four touchdowns, and Cowboys quarterback Tony Romo threw for 506 yards and five touchdowns.

Despite having one of the greatest statistical games by a quarterback, Romo ended the game by living up to his reputation as a choke artist. With the score tied, and only minutes remaining, the Cowboys had the ball and a chance to drive down the field and give the Broncos their first loss of the season. The first play of the drive, Romo was sacked for a six-yard loss. The second play, Romo threw an interception. Denver went on to win by a field goal.

If Romo can shake off his reputation for choking, and go out and execute in big games throughout the remainder of the season, then he may just be named among the elite quarterbacks in the league. Until then, however, people will always doubt him.

Week six has much to look forward to

With NFL records on the line, undefeated seasons at stake, every week is something to look forward to. When realizing that Terrelle Pryor and the Raiders will be taking on Alex Smith and the Chiefs, and Tom Brady and the Patriots set to take on Drew Brees and the Saints, week six looks to be every bit as exciting as week five.