As New England stops dreaming about an undefeated Super Bowl repeat and worries about its defense, Kansas City suddenly can be a lot more confident that it finally has the offensive firepower to win it all.

Hunt on Thursday provided plenty of new juice on the field. But for Smith, there also was a source of fuel on the sideline — Patrick Mahomes.

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Smith turned in his best high-volume passing performance as a Chief (28 of 35, 368 yards passing, four TDs, 148.6 rating). It marked only the sixth time in four-plus seasons with Kansas City, including playoffs, that he’s thrown for 300-plus yards in a game.

Hunt accounted for 98 of those passing yards and half of those scores as part of a record-setting rookie debut, totaling 246 yards from scrimmage. The RB’s 78-yard TD catch and run was preceded by receiver Tyreek Hill speeding by the Patriots’ secondary for a similar, 78-yard TD.

In the past, with go-to tight end Travis Kelce bottled up — as he was Thursday with former top wideout Jeremy Maclin no longer on the team — Smith would have been lost in a dinking and dunking haze, capped by the conservative play-calling of coach Andy Reid.

Instead, after he got Smith comfortable with a diverse, well-paced scoring drive to tie the game 7-7 in the first quarter, Reid let his QB loose in ways we haven’t seen.

After thinking about what could have been in frustrating, one-possession playoff losses to the Patriots and Steelers the past two seasons, respectively, the Chiefs knew they needed to be more efficient and explosive on offense. Getting a versatile, elusive back to reboot post-Jamaal Charles was a must, and Hunt checks all the boxes.

With Hunt’s potential to be the new top backfield target for Smith, the Chiefs are set up to have a third ideal passing dimension behind the athletic mismatches of Kelce and Hill, something Maclin couldn’t provide.

The best way to outscore the Patriots is to do what they do: Confuse them with options all over the field. (Before the Falcons fell in Super Bowl LI, they were doing just that.) To that end, the Chiefs stealing Hunt in the third round of April’s draft was critical, and it paid off immediately Thursday.

But just as key to helping Smith is the Chiefs’ first-round pick, Mahomes.

Kansas City’s selection of a high-upside, big-armed QB surprised many and brought into question how much longer the Chiefs wanted to go with Smith — and whether they had hit a ceiling with him. After all, it happened to Smith once before in San Francisco, where Jim Harbaugh went with the upside of Colin Kaepernick over him.

But credit Reid for never hinting that Smith’s starting job was in danger, and also realizing it doesn’t hurt to have Smith further motivated by competition.

Mahomes showed off his raw rifle of an arm during the preseason. Smith responded Thursday, perhaps wanting to shred the dreaded “game manager” label for good as a passer possessed.

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With all the hype and buzz around Tom Brady being better than ever at age 40, Smith was at his smoothest. He needed to be smooth for the Chiefs to pull away in a shootout and let their defense, arguably the AFC’s best, do the rest.

With that defense possibly losing its leader Eric Berry to an Achilles injury for a while, a rejuvenated, revved-up Smith becomes all the more important. Despite Kansas City having won the AFC West last season, Oakland has been cited as the division favorite because of the QB edge with Derek Carr. But with Smith this driven, the Chiefs’ outlook changes.

A loss and a shaky Smith outing would have been disastrous. A win and a spectacular Smith? The Chiefs could not have asked for a better beginning.