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For the second year in a row, the 49ers are knocking on the door of the Super Bowl. Last season, their dreams of a title slipped through their fingers as they couldn't hang on to their fourth-quarter lead over the eventual-champion Rams

Fast forward to this year's campaign, and you'll find a lot of the same stars like Nick Bosa, Deebo Samuel, George Kittle and head coach Kyle Shanahan manning the sideline. However, the quarterback position has gone through the wringer as Trey Lance and Jimmy Garoppolo both have been put on the shelf due to injury. That thrust Mr. Irrelevant, Brock Purdy, into the limelight, and the rookie has not only kept San Francisco above water but has them on the doorstep of a Super Bowl berth. 

So, how do the Niners avoid coming up just short of the big game like they did a year ago? Below, we'll highlight three things that need to happen to ensure that San Francisco not only gets to Super Bowl LVII, but is hoisting the Lombardi Trophy by the end of it.  

Brock Purdy continues his Cinderella run

As the pressure builds with each passing game, there is the thought in the back of folks' minds about whether or not the next game will be the one where Brock Purdy turns into a pumpkin. After all, no rookie quarterback has ever brought his team to the Super Bowl before, and each of the four previous rookie signal-callers to reach the conference title game have lost while collectively throwing more interceptions than touchdowns. That freefall is what Purdy and the Niners will need to avoid for the young quarterback to make history and have the franchise win its sixth title.

Fortunately for San Francisco, Purdy has yet to show us that the moment is too big for him. Since stepping in as the starter following Garoppolo's foot injury, he has played at an elite level. Since his first career start for the club in Week 14, Purdy has an NFL-best 116.0 passer rating. That's the highest passer rating by a 49ers player over a seven-game stretch since Steve Young in 1996-97. The 49ers are also averaging 32.6 points per game and 8.98 yards per attempt since Purdy took over as the starter, which are both tops in the NFL. Purdy has also been smart with the football, totaling just two turnovers in his seven starts, which includes zero in the postseason. 

With many young quarterbacks, you'll oftentimes see a "deer in the headlines" look from them at some point or another, but Purdy hasn't shown much panic. In fact, he's played extremely well when things either break down or he faces a "gotta have it" moment. On extended plays that take three or more seconds for the ball to be thrown, Purdy has 10 passing touchdowns and a 132.5 passer rating since Week 14.

Purdy also boasts a 114.7 passer rating and a 5-0 touchdown-to-interception ratio on third down since he's become the starter. If he can maintain this level of play and doesn't have that feared rookie collapse, he is playing like a Super Bowl-caliber quarterback.

Defense doesn't get beat deep

By most measures, San Francisco's defense is the gold standard in the NFL. The 49ers rank No. 1 in the league in DVOA, have superstars like linebacker Fred Warner and pass rusher Nick Bosa and are dominant against the run. That said, this unit doesn't come without any flaws and its one weakness will be one that can't be exposed if it wants to win it all. 

The dirty little secret about this defense is that you can throw deep on them. On throws 25 or more yards downfield, this 49ers defense ranks 25th or worse in the NFL in completion percentage, touchdown-to-interception ratio and passer rating. Against wide receivers, the unit is 25th in yards per attempt allowed as well. San Francisco has allowed a 100-yard receiver in three of its previous four games (including playoffs). In the postseason, the defense has seen D.K. Metcalf catch 10 balls for 136 yards and two touchdowns during Super Wild Card Weekend and then allowed CeeDee Lamb to catch 10 passes for 117 yards in the divisional round.

With the Eagles -- who love to throw it deep with Jalen Hurts and A.J. Brown -- standing in their way to reach the Super Bowl, and then either Joe Burrow's Bengals or Patrick Mahomes' Chiefs waiting for them in Phoenix if/when they get there, that flaw is one that could prove fatal if the 49ers' defense doesn't keep it in check. For them to win it all, they'll have to see better play in the secondary or hope that Purdy and the offense can match those scores if they are gashed on chunk plays through the air. 

Christian McCaffrey remains lightning rod of the offense

While Purdy certainly deserves his flowers for what the rookie has been able to do after being thrust into the starting role, Christian McCaffrey's injection into the offense can't be overlooked either. Since coming over during a mid-season trade with the Carolina Panthers, McCaffrey has been a lightning rod for San Francisco, which has won every game he's started since the back arrived. 

Over this 12-game winning streak, McCaffrey has averaged 111.8 yards from scrimmage and 12 total touchdowns. That scoring output is tied for No. 1 in the NFL over that stretch, while his yards from scrimmage average ranks third, and his 19.5 touches per game is tied for fifth. McCaffrey has also gone eight straight games with a touchdown, which is the longest streak by a 49er since Terrell Owens in 1998.

McCaffrey's versatility as a pure runner on top of his skills as an elite pass catcher out of the backfield gives this 49ers offense a dynamic chess piece to pair alongside Deebo Samuel and makes life easier on Purdy. 

The big concern surrounding McCaffrey -- and has been the case for the past few years -- has been his health. He did seem to tweak his calf against Dallas in the divisional round which forced him to miss the bulk of the fourth quarter. So long as he can remain healthy and be on the field for San Francisco, the Niners will have a game-breaking talent that can turn the game on its head with one touch.