What’s the difference between a legendary young quarterback and a work-in-progress QB whose forgettable final quarter will be endlessly scrutinized in the offseason? In some cases, it’s just a matter of a few inches ….

SEATTLE — Colin Kaepernick overcame a deafening din, two fourth-quarter turnovers, the NFL’s top-ranked defense and his tortured history at CenturyLink Field to add to his remarkable postseason portfolio Sunday night.

On a play that will reside in franchise history alongside The Catch, Kaepernick tossed a daring 18-yard touchdown to Michael Crabtree in the right corner of the end zone with 22 seconds left to give the 49ers a 24-23 win over the Seahawks in the NFC Championship Game.

The 49ers will meet the Broncos in Super Bowl XLVIII in East Rutherford, N.J., on Feb. 2.

“Clutch,” a wild-eyed Jim Harbaugh said of Kaepernick’s performance. “Clutch! Clutch! Clutch! Clutch! I mean, really, who in the world does it better than Colin Kaepernick?”

Kaepernick, who led the 49ers back from a 17-0 second-quarter deficit in last year’s NFC title game, authored an even more indelible comeback Sunday night.

Kaepernick’s game-winning throw sailed a whisker over the outstretched left arm of 6-foot-3 All-Pro cornerback Richard Sherman and capped a masterful nine-play, 78-yard drive that began with 3:32 left. On the march, Kaepernick completed 6 of 7 passes for 74 yards, converting a 4th-and-2 with a 17-yard pass to Frank Gore and delivering a 16-yard strike to Crabtree on 3rd-and-2 with a minute left.

Kaepernick lost a fumble and tossed an interception on the previous two drives, but those errors didn’t deter him from challenging Sherman with the season teetering in the balance. A Wisconsin native who grew up idolizing Brett Favre, Kaepernick channeled the Old Gunslinger by floating a fade Crabtree collected despite being blanketed by Sherman, a first-team All-Pro the past two seasons who led the NFL in interceptions in 2013.

The throw, which Kaepernick determined would be tossed to Crabtree even before the snap, was seemingly brazen given the situation. It was first down and the 49ers still had two timeouts and 30 seconds left. Why challenge Sherman with such a risky throw?

“I had a one-on-one matchup with Crab,” said Kaepernick. “I’ll take that every time, against anyone.”

The pass evoked memories of his ill-fated, fourth-down fade to Crabtree in the final minute of last season’s Super Bowl. But Kaepernick clearly wasn’t concerned with the past Sunday at the stadium where he’d committed five turnovers and the 49ers had lost by a combined score of 71-16 in his previous two starts.

Kaepernick’s about-face included the longest run by a quarterback in NFL playoff history (58 yards), the second-most rushing yards by a QB in the postseason (130) and a you’ve-got-to-be-kidding-me 26-yard, jump-pass touchdown to Anquan Bolin that gave the 49ers a 17-13 lead in the third quarter.

Despite starting just six postseason games, Kaepernick has three of the top five rushing performances by a quarterback in the playoffs, including the top two.

Sunday’s coolly orchestrated comeback came with the NFL’s loudest crowd providing the ear-splitting soundtrack and was reminiscent of his earlier postseason heroics: In a 23-20 wild-card win at Green Bay, he directed must-have scoring drives on the 49ers’ final two possessions at near-sub-zero Lambeau Field.

With his latest win, he improved his postseason road record to 4-0. His Hall-of-Fame predecessors, Joe Montana and Steve Young, were 1-6 in such situations.

Colin Cool? Captain Clutch? Mr. January? Those monikers were fitting Sunday night for a quarterback who has more NFC title-game comebacks than full seasons as a starting NFL quarterback.

Said Kaepernick of his mindset before he embarked on a historic drive: “That we were going to go win it.”