The San Francisco 49ers have been the surprise team of the year. Even if you thought they were going to be really good, you probably didn't have them at 7-0 through the first eight weeks of the season… and neither did the Arizona Cardinals.

In fact, San Francisco is one of only two undefeated teams left (the New England Patriots are 8-0). What's even crazier, is they don't appear to be slowing down.

The 49ers had their most impressive win of the season in Week 8. They squared off with the 4-2 Carolina Panthers, a team on a four-game winning streak. San Francisco didn't even flinch, demolishing the Panthers by a final score of 51-13.

Now they face off with NFC West division rivals, the 3-4-1 Arizona Cardinals. If the 49ers are to win and remain undefeated, here are four reasons why that will happen.

Nick Bosa

nick bosa

Nick Bosa had not disappointed through his first six games in the NFL. The second-overall draft pick had four sacks, a forced fumble and a fumble recovery. Things were going great.

Then came along Week 8, and Bosa went ballistic. The rookie recorded three sacks and an interception, becoming the youngest player to ever do that in a single game.

Not only did it easily thrust Bosa to the top of the defensive rookie of the year conversation (and into the defensive player of the year one) but it helped get San Francisco to 7-0.

He now has seven sacks, one forced fumble, one fumble recovery and one interception. And he's done all of that in just seven games.

Even scarier, he's getting hot. The week before the 49ers played the Washington Redskins. In that game, Bosa recorded a sack and three tackles for loss. That included a game-clinching play.

He's quickly become an MVP of the team and with Arizona's offensive line being questionable, Bosa could put up big numbers in Week 9. Don't be surprised if he finds himself as a main reason for another 49ers win.

Running Game

The running attack of the San Francisco offense has been absolutely deadly this year. A three-headed monster of Tevin Coleman, Matt Breida and Raheem Mostert has been fantastic.

Week 8 served as a notice to the entire NFL that they meant business. Breida only had 35 yards on 11 carries (15 yards on one reception as well). He's been great all year though so he gets a pass.

Meanwhile, Mostert had 60 yards and a touchdown on just nine carries.

The show stealer was Coleman in Week 8 though. He ran for 105 yards and three touchdowns on 11 carries. He also had two receptions for 13 yards and another touchdown on the night.

Having three ultra-talented running backs means the 49ers can always have fresh legs. The fact that none of them had to run the ball more than 11 times proves that they can be crazy productive without having to run them into the ground.

That will serve the 49ers well in Week 9. Attack the Cardinals defense consistently with a strong running game could be a major key to victory.

Defense

Richard Sherman, 49ers, Redskins

What else is there really to say about this defense. Obviously Bosa has already been talked about. He's not the only reason the San Francisco defense has been as good as it has been though.

The entire defense has been superb. They allow an NFL low 224.4 yards per game. Meanwhile, the 11 points per game that they've allowed is second lowest only to the New England unit that is allowing just 7.6.

Arizona's offense can show big signs of life with Kyler Murray at quarterback. He's shown an ability to make plays out of nothing and his arm has been fantastic.

That being said, he's still a rookie quarterback with a sub-par offensive line and some questionable help around him.

It is definitely a recipe for success for the San Francisco defense. When they are on top of their game, good luck scoring against them. And if you don't score, you don't win.

Jimmy Garoppolo

Jimmy Garoppolo, 49ers, Redskins
CP

A lot has been said about quarterback Jimmy Garoppolo. Many believe he's extremely overrated and overhyped. To be fair to them, the media did crown him as the next big thing after leaving the Patriots.

So far, his record has lived up to the hype. The numbers haven't exactly been there though. While the completion percentage is solid (69.8%), that's about it.

Through seven games, Garoppolo has 1,489 yards and nine touchdowns. That puts him on-pace for 3,403 yards and 21 touchdowns, not exactly inspiring. Meanwhile, he has seven interceptions and four fumbles. Not good numbers either.

However, Garoppolo has looked really sharp at times and has proven he can do enough to lead the offense. This is more of a defensive team and a running offense anyways. All Garoppolo has to do is make a few plays a game. So far, he's done that.

Now he's going up against a defense that has looked really bad for most of the season. He could use this as an opportunity to prove he can be a great quarterback in the NFL. A big game from him almost certainly leads to a win for the 49ers.