When he needed to step up and have one of the biggest games of his 12-year NFL career Thursday night, Kansas City Chiefs' quarterback Alex Smith delivered for the entire country to witness.

Outdueling a future Hall of Famer in Patriots' quarterback Tom Brady, Smith completed 28 of 35 for 368 yards and four touchdowns against the New England Patriots in Foxboro to help the Chiefs to a dominant 42-27 victory.

Coming into the game, the Patriots had lost just once to an AFC team at home since 2007 with Brady under center. That's what Smith and the Chiefs were up against.

So, it was a big moment for the Chiefs and for Smith, who admitted afterwards that there was something extra about this game compared to other season openers because of all the pregame festivities and the fact that it was the NFL's opening game of the 2017 season.

"This one probably more than any other I have been a part of because you're kicking off the season and playing the defending the world champions," Smith said after the game.

Despite falling behind early against a Patriots' team that was 90-1 at home when leading by 10-plus points since 2001, Smith helped keep the offense together and answered back several times in the first half.

"He doesn't get frantic much," Chiefs coach Andy Reid explained of Smith. "He comes out poised and it's good for the young bunch around him—the young receivers and the young running back. He calms the storm and he doesn't get overwhelmed."

That character and resolve were never more evident than the Chiefs' second offensive drive of the night, which followed an impressive fourth-down stand by the defense.

Leading up to that stand, everything was going the Patriots' way. They had scored on their first offensive possession to take a 7-0 lead and took less than three minutes off the clock to do so, and then Chiefs' rookie running back Kareem Hunt fumbled on the Chiefs' first offensive play of the night.

The crowd was going nuts and everything was working against the Chiefs.

Then, the Chiefs' defense stood tall and stopped the Patriots short on fourth down, which was one of the turning points in the game because of how Smith helped settle the offense down on their next drive.

On the ensuing drive, Smith led the Chiefs on a 12-play, 90-yard drive that culminated with a 7-yard touchdown pass to tight end Demetrius Harris on third-and-goal.

Smith was 7 of 8 for 66 yards on the drive, which tied the game, 7-7. The only incompletion he threw on that drive was actually a throw-away.

Coming into that game, the Patriots hadn't allowed a 90-yard drive at home in more than four years, and Smith actually led the Chiefs to three of them on the night.

And two of the three long scoring drives didn't take all that long, and each gave the Chiefs a lead.

Early in the third quarter with the Chiefs trailing, 17-14, Smith found second-year playmaker Tyreek Hill deep down the field to give the Chiefs their first lead of the game.

"It was kind of a combination two things at the line (of scrimmage)," Smith explained of the play. "We made a great protection adjustment. We got the nickel off the slot and those guys picked it up, Travis Kelce grabbed the safety and that left Tyreek outside one-on-one, and not many people can run with him.

"For me, I just put it out there."

Hill's double-move on an out-and-up created some confusion in the Patriots' secondary and Smith placed the ball perfectly to Hill down the field for a 75-yard touchdown.

The play also made NFL history as Hill became the first player to ever have touchdown plays of 60-plus yards in five-consecutive regular season games.

And it wouldn't be long before Smith would strike again deep.

Early in the fourth quarter, Smith found Hunt deep down the middle for a 78-yard touchdown, which once again gave the Chiefs the lead at 28-27.

"I was happy he saw the same thing I did as I brought him into the middle of the field because you just don't know how that's going to shake out with the motion at the snap," Smith explained of the touchdown to Hunt. "I thought it was a great adjustment by him."

"I had to beat the guy with speed," Hunt added of the play. "Alex made a beautiful pass and I was like, 'I can't drop this,' and I just knew we had to go get points. We were down and I knew we had to get seven points on the board, so I was just running my fastest and hardest."

Smith spoke about Hunt, who set an NFL record for a rookie running back by putting up 246 total yards from scrimmage in his NFL debut, after the game.

"There was a good chunk there where we were going as Kareem was going," Smith said. "He was really a big chunk of the offense tonight. For a young guy, we put a lot on him in all facets of the game plan tonight and he was able to handle it.

"Certainly, hats off to him in both of those areas – not just physically – he was able to handle the game plan. That's a credit to him." 

With a receiver corps that has an average age of 23.5 years old, and a starting running back in Hunt who is just 22, Smith has a lot on his plate to help bring along and mentor the young playmakers around him, particularly in an environment like the Chiefs played in on Thursday night.

"I'm definitely an old guy for sure on the offense," Smith said after the game. "There's an energy with those young bucks. There's something about them especially when you get them all together. They just go and they feed off each other. The playmaking becomes infectious. Each guy wants to be the next guy to make the play and they've all got big old grins on their faces most of the time when you step in the huddle.

"There's something about that. They love playing ball."

Despite the impressive victory, which moving forward will probably earn the Chiefs much more respect nationally, Smith isn't making it any more than what it is in the bigger picture.

"I think you have to be able to handle defeat, as well as victory, the right way, and I think each can deter you because you put a lot of emotion into it," Smith said. "You certainly get this victory, but you can't forget that it's 1-of-16, right? You've got to keep that same mentality week in and week out – the attention-to-detail mentality.

"Just because you do it one night, doesn't mean it will just carry over. You have to find a way to beat the next opponent and the unique challenge they present."

It's easy to see why Smith is one of the unquestioned leaders of this team.