From 1-5 to a playoff berth isn't just a really good story; it's a historically great story.

The Kansas City Chiefs join the 1970 Cincinnati Bengals as the only teams in NFL history to begin the season with a 1-5 record and then earn a playoff berth.

One of the main reasons the Chiefs are in this position has been the play of quarterback Alex Smith, who once again led the team on Sunday during their 17-13 win over the Cleveland Browns to earn their ninth consecutive victory, which ties a franchise record (2003, 2013).

Smith finished the game 15 of 22 for 125 yards with 2 touchdowns and 1 interception, also adding 6 rushes for 54 yards on the ground. The performance helped him set a couple of career highs in terms of yards through the air and on the ground this season.

Before 2015, Smith's best season throwing the football was back in 2013—his first year in Kansas City, when he threw for 3,313 yards with 23 touchdowns and 7 interceptions.

Through 15 games this season, Smith has already eclipsed that total with 3,330 yards passing, but his 7.47 yards per attempt also ranks as best of his career in seasons he's played in at least 11 games. He's thrown 18 touchdowns to just 5 interceptions.

Much of Smith's success this season can be traced simply back to continuity within the system.

In his first eight years as a professional quarterback, Smith played for three different head coaches, seven offensive coordinators and six quarterback coaches.

In Kansas City, he's had the same three guys in each of those positions in the three years he's been with the Chiefs: Andy Reid at head coach, Doug Pederson at offensive coordinator and Matt Nagy as his quarterbacks coach.

"Nobody works harder, first of all," Chiefs coach Andy Reid mentioned of Smith on Monday. "I mean, he's a brilliant guy, but just the consistency of being in the same offense, doing the same things – you can see the comfort that he's got there."

Smith has been comfortable when the pressure has been on this season, both in terms of beating the blitz and during the fourth quarter. Smith has completed 68 percent of his passes with 9 touchdowns and just 1 interception against the blitz, and he has completed 65 percent of his passes with 6 touchdowns and just 1 interception in the fourth quarter, also averaging more than 8 yards per attempt in the final 15 minutes of the game.

Smith already broke a franchise record earlier this season with 312 consecutive passes thrown without an interception, which also stands as the second-best mark in NFL history (Tom Brady, 358).

Much has been made of his risk-averse nature, which can also be described as making the correct decision on any given play, something Reid praised of his signal caller.

"He's playing at a very high level right now," Reid added of Smith. "I don't worry about [whether he's making the right decisions]. He's got good judgement on things."

One of the best passes Smith has thrown this season came on Sunday against the Browns, when he fired it through a small window for an 11-yard touchdown to veteran Jeremy Maclin, who eclipsed 1,000 yards for the season on that play.

"That's about as tight a window as you're going to have – he has to fit it in between the safety, the corner and then that linebacker," Reid explained. "That's kind of splitting that triangle right there.

"There's got to be a massive amount of trust there."

Smith has been trusting his receivers to make plays for him this season as he's had 31 passes that have gone for at least 25 yards, which is the most he's had in any season in his career.

Also, according to the folks over at ESPN Stats and Info, Smith has been taking more shots down the field recently.

Smith has started to air it out with an average pass distance of at least 8 yards downfield in three of his last five games. He has 15 completions and 5 touchdowns on passes thrown more than 10 yards downfield during that time.

Smith's QBR rating of 83.1 since Week 7 is second-best in the NFL during that time, according to their rankings.

He's completed 13 of 32 passes for 412 yards with 3 touchdowns and 1 interception on passes that have traveled at least 21 yards in the air, which is a stark improvement from the 3 for 18 he had last season.

Another area we've really seen Smith really begin to trust himself over the past several games is when he decides to take off and run with the football.

Since Week 7, Smith has scrambled for 271 yards, which is 40 more than any other player in the NFL during that time, according to that same ESPN article.

Smith has rushed for 437 yards this season, which is a career best and also a franchise record for a Chiefs quarterback. It also ranks as the fourth-most for a quarterback in the NFL this season.

Reid mentioned that Smith has an innate ability in knowing when it's best to tuck and run after he drops back and surveys the defense.

"He knows where the seam on the front is going to be so he can get through," Reid explained, "and then he knows what's being accomplished by the route. If you go back and look, there are a couple guys that are open on shorter routes, but [Alex] knows that the defense has been cleared out in a certain area where he can maybe maximize what that route was going to take place.

"He's got kind of a sixth sense there with that, which is a pretty good deal to have."

After losing arguably their best offensive player in running back Jamaal Charles back in Week 5 against the Chicago Bears, the focus and pressure was put on Smith to lead this team to a historically great finish, which is exactly what he's done after nine straight wins and career marks in terms of yards passing and rushing.

Smith will now lead this team to the playoffs for the second time in his three years in Kansas City.

Pretty impressive.