FOXBOROUGH, Mass. — The game the Kansas City Chiefs had been waiting for nearly nine months was barely five minutes old, and already they were flirting with being blown out — and the defending champion New England Patriots knew it.

That’s why, with 9 minutes and 34 seconds left in the first quarter of the NFL’s season opener Thursday, the Patriots and coach Bill Belichick— who had just been gift-wrapped a Kareem Hunt fumble and led 7-0 at that point — decided to go for it on fourth-and-1 at the Chiefs’ 10-yard line.

The crowd at Gillette Stadium rose to its feet, hopeful the champs — who had just raised their fifth Super Bowl banner — potentially could deliver another lethal strike that could put the Chiefs on their heels in front of a nationally-televised audience.

But here’s the thing about talented, battle-tested teams like the Chiefs: Where other teams falter, they often find a way to steady. Where other teams break, they simply bend.

So when the Chiefs proceeded to snuff out the Patriots’ ensuing running play well short of the marker — and give the ball back to their offense, energy in the stadium sapped — it served as an early reminder that this 12-4 team a year ago remains mentally tough.

Tough enough to pull off a 42-27 victory.

The offense, suddenly energized by the stop, went on a 12-play, 90-yard scoring drive that featured some hard, darting runs by Hunt, and some efficient, precise passes by quarterback Alex Smith, who executed Reid’s play calls — which featured lots of personnel groupings and plenty of wrinkles — to perfection. The drive culminated in a short touchdown pass to tight end Demetrius Harris that knotted the game up at 7-7.

And while the Patriots would follow with a field goal on their next drive, it might as well have counted as a win for the Chiefs. Facing a fourth-and-1 at the Chiefs’ 8, the Patriots — instead of going for it this time — opted for the easy three points.

It was, perhaps, the clearest sign that the Chiefs would not be outclassed in this one. The Chiefs were in Foxborough to win, and they would not go down quietly.

This again proved to be the case when, late in the second quarter, the Chiefs — who trailed 17-7 — forced a rare Patriots’ three-and-out and proceeded to use a short-to-intermediate passing game to mount an impressive 12-play, 92-yard scoring drive in only 2 minutes, 34 seconds to cut the halftime deficit to three.

And this also proved to be the case when, early in the third quarter, Smith — who is known for his risk-averse nature — quieted his critics with a gorgeously-thrown deep ball to his new No. 1 threat, second-year speedster Tyreek Hill, who tracked the ball with ease and scored with gobs of yards between him and the closest defender.

The score gave the Chiefs a 21-17 lead midway through the quarter, a scenario that seemed unlikely in the opening moments of the game.

The lead would not prove to be safe — the Patriots quickly retook the lead with a scoring drive, and extended it with a field goal that put them ahead 27-21 entering the fourth quarter — but again, there was no quit on the Chiefs on this night.

And Smith — the quarterback who has compiled a 41-20 starting record from 2013 to 2016 but has often found himself criticized for a lack of downfield efficiency — was the main reason why.

On the Chiefs’ very next drive, Smith uncorked another gorgeous deep ball, this time to Hunt, for a 78-yard touchdown pass over the middle that stunned the Gillette Stadium crowd and gave the Chiefs a 28-27 lead with 14 minutes left in the game.

Smith’s line at that point — 23 of 28 for 312 yards and four touchdowns, no picks — was impressive.

There was still plenty of football left to play, of course. But his flashes of dynamism — not to mention the mental toughness the team flashed throughout, starting with the defensive stand early in the game — were perhaps the most encouraging signs for Chiefs fans hoping to see their team not only win the AFC West again, but also take that next step toward finally reaching the Super Bowl for the first time since 1969.