The 28-year-old finished the game against the Rams with three touchdowns, 346 passing yards and no interceptions.
Darnold’s gripping slugfest with Stafford was effectively tilted in Seattle’s favour when a late Rams drive to the Seahawks’ six-yard line came away with nothing.
“We came here with expectations to win,” Rams coach Sean McVay said afterwards.
“It was a great back-and-forth game by two great teams, but a couple of critical errors ended up costing us ... I’m never really short on words, but I am right now. It’s tough, but this is sports and you’ve got to be able to deal with it.”
Seattle, meanwhile, were left looking ahead to a Super Bowl clash with the Patriots in Santa Clara, California, on February 9 (NZT), 11 years after losing to New England in the NFL showpiece in 2015 during the Tom Brady era.
The Patriots are targeting a record seventh Super Bowl following their gritty, low-scoring victory in Colorado.
The AFC title game played out in brutal conditions, with the field gradually becoming blanketed in snow as a storm swept over the venue.
New England quarterback Drake Maye held firm after a shaky start, leading the Patriots upfield for the decisive field goal after rushing for a first-half touchdown.
“We battled the elements,” said Maye.
“These conditions, it’s not great throwing the football. But hey, we do what we need to do ... We’re off to the Super Bowl. Let’s go!”
The win cements a remarkable resurgence for the Patriots.
After the dominant era of the Brady dynasty that yielded six Super Bowl titles, New England have endured a painful rebuild.
But under new head coach Mike Vrabel they were a revelation this season, topping the tough AFC East for the first time since 2019.
“Just so happy for Mike Vrabel, former teammate of mine,” said Brady, now working as a commentator for Fox television.
“Went to New England, no one was quite sure how they’d do (after) back-to-back 4-and-13 seasons, and they turn it into a road AFC victory in Denver. I know how hard that is.”
The Patriots, who already boasted the most Super Bowl appearances with 11, will now have their 12th showing on American football’s biggest stage, and a chance to vie for a record seventh Lombardi trophy.
Vrabel, who won three Super Bowls playing alongside Brady for the Patriots, would be the first person to win the sport’s ultimate prize as a player and coach for the same franchise.
“I won’t win it – it’ll be the players that will win the game, I promise you,” Vrabel said post-match.