During the previous four games for the Kansas City Chiefs, all wins, the defense had allowed an average of less than 10 points per game.

The offense had also outscored their opponents 64-9 in the first half.

They were dominating from the onset.

So in regards to the offense, they were never really challenged to throw a counterpunch in order to come back in a game. They were always ahead.

That wasn't the case on Sunday, when the Chiefs fell behind early against the Buffalo Bills by a score of 10-0 and managed just 29 yards of offense in the first quarter.

Nothing was going right.

So when compared to the 183 yards the Bills had put up in the first 15 minutes of the game, the offense had its back against the wall and was going to be challenged to do something they hadn't had to do during their four-game winning streak.

It was their chance to carry the team to a victory, and on a rainy, freezing day at Arrowhead Stadium, the odds didn't look good early.

That put the onus squarely on the shoulders of quarterback Alex Smith.

In his biggest game of the season and when his team needed him to lead them from behind, Smith came through for the guys who have stood by him from the beginning.

"We're lucky to have him here," Chiefs coach Andy Reid said of Smith on Sunday. "He's a heck of a player, great person, good leader, and you just saw it. He does whatever we need him to.

"He gets it done."

Smith finished the game 19 of 30 for 255 yards and 2 touchdowns, adding 35 yards on the ground as well.

Perhaps the most compelling aspect of Smith's game on Sunday were the connections he made with receiver Jeremy Maclin on three key vertical passes—an area of Smith's game he's had to answer plenty of questions about throughout his career.

"We had some opportunities earlier in the year on some deep balls and just missed them," Smith explained after the game. "[Maclin] has done a great job of just continuing to win out there and staying hungry. I was finally able to connect with him today and give him an opportunity."

Going into Sunday's game, Smith knew from studying the Bills throughout the week that opportunities to make plays down the field with Maclin were going to be available.

"That was a matchup we talked about all week," he said. "I felt good about the opportunity and Jeremy is a type of player that is going to win those battles."

"[Bills head coach] Rex Ryan is very respected around the league and he likes to do what he likes to do," Maclin explained of the Cover-1 looks they knew they'd get. "We were able to take advantage of that a little bit today."

The first of three key plays for Smith and Maclin was on the fourth offensive drive of the game, after the first three drives yielded just 29 total yards on 10 plays.

At this point, the momentum was all on the other side of the field with the Bills.

After a couple of nice runs from running back Spencer Ware gained 22 yards and gave the offense a much-needed spark, Smith and Maclin built that flame with a 37-yard hookup that saw Maclin make a nice sliding catch down the field.

The chunk play had nearly doubled the offense's production to that point, and Ware took the next play 3 yards for the touchdown run to get the Chiefs on the board.

The Bills responded with a drive of their own culminating with Sammy Watkins' 21-yard touchdown reception. The catch capped off a 6-catch, 168-yard, 2-touchdown first-half performance from the former No. 1 pick.

The Chiefs finally had some life after Smith's connection to Maclin that set up Ware's touchdown. The score brought them to within 3 points at 10-7 with 2:35 left in the first half and things were looking good. But just like that, they were down 16-7 and their momentum was quickly taken away after Watkins' touchdown.

Therefore, it was up to Smith to respond, again, and this time it was coming in the 2-minute situation, in which throwing the ball down the field is key in having any kind of a chance to score.

Two plays into the drive, the first of which was a 14-yard hookup to Maclin, the Bills gave them a single-high, cover-1 look on first-and-10 from the 41-yard line.

It was a look they were prepared for and one that would give Maclin a one-on-one opportunity.

After taking the snap out of shotgun, Smith looked left and moved the safety, then dropped a dime over the shoulder and deep down the right sideline to Maclin, who had a step on standout rookie cornerback Ronald Darby.

The 41-yard touchdown was a huge play, and it may have brought the score to 16-14, but it seemed like much more than that for Smith.

It was a response to not just a touchdown by the Bills on their previous drive, but also to those wondering if he could lead them to a big score in this kind of a situation.

When you add in the fact that there were less than 2 minutes on the clock and he had done that on their previous drive as well, the meaning was more than a couple of nice passes.

It was proof of what those around him have been saying the entire time—that he could do this when needed.

Smith's reaction after that touchdown showed what it meant to him.

"I always feel like I celebrate pretty big, at least on the inside," Smith said of his reaction to that touchdown to Maclin. "I was pretty jacked up there with where the game was at and then to hit that right before half was a big play."

While a couple of nice throws are helpful, they were still behind and simply getting them close wasn't going to cut it. 

On the first drive of the second half and trailing 16-14, Smith and Maclin connected for another big play.

This time, Maclin was lined up in the slot and with an outside release, got a half-step on cornerback Stephen Gilmore. Maclin made a fantastic diving catch as Smith put the ball where only Maclin could make a play.

The result was a 32-yard gain.

Two plays later, Smith found Kelce across the middle for a 15-yard touchdown.

Smith had made three vertical throws to Maclin when the Chiefs were trailing to lead them back from a 10-0 deficit to take a 21-16 lead.

The Chiefs finished the game with five plays of 32-plus yards, including the three deep passes to Maclin.

Maclin finished the game with 9 catches for 160 yards and a touchdown, which is just the third time in his career he's had that many yards in a game.

Over the past five years, the Chiefs have had four players gain at least 140 yards receiving in a single game, and Maclin has three of those games this season.

But much like Smith, Maclin doesn't care about numbers.

"It's not about stats. It's not about catches. It's not about yards, it's about being there when your team needs you."

On Sunday, the Chiefs needed Smith and he came through.

On the final play of the third quarter, Smith's legs and willingness to take a hit in the effort to gain a first down were on display in another key situation.

On third-and-11 from the Buffalo 34-yard line, Smith dropped back to pass, scanned the field and decided he had a better chance to pick up the first down if he was to tuck it and run.

A few yards shy of the first down with defenders approaching, Smith could have slid and avoided contact. Instead, he tucked his head and lunged forward, taking a hit and picking up a first down in the process. 

It was one of the key plays in the game and set up Cairo Santos' 38-yard field goal that gave the Chiefs a 27-22 lead early in the fourth quarter.

Effort and playmaking when called upon defined Smith's game on Sunday—a game that answered questions for those who didn't already know. "He does whatever we need him to," Reid said. "He gets it done."