The Seattle Seahawks mixed their typically rugged defense with a few big plays on offense to secure the second Super Bowl berth in franchise history. They overcame an inglorious start and an early 10-point deficit, then hung on in the final seconds to beat the San Francisco 49ers, 23-17, on Sunday in an intense and combative NFC championship game.

Linebacker Malcolm Smith’s end-zone interception sealed the outcome with 22 seconds remaining. The 49ers, seeking a winning touchdown, had driven to the Seattle 18-yard line. But quarterback Colin Kaepernick’s pass intended for wide receiver Michael Crabtree was deflected by cornerback Richard Sherman and grabbed by Smith.

“I expected that from our defense,” Seahawks wide receiver Doug Baldwin said. “When there’s a crucial situation, they’ve always made plays like that. . . . It’s no fluke. That’s what they’ve been doing all season.”

Sherman was more emphatic, saying: “I was making sure everybody knew that Crabtree was a mediocre receiver. Mediocre. And when you try the best corner in the game with a mediocre receiver, that’s what happens.”

Tailback Marshawn Lynch ran for a third-quarter touchdown and quarterback Russell Wilson threw a fourth-quarter touchdown pass to wide receiver Jermaine Kearse for Seattle. Place kicker Steven Hauschka provided three field goals. The defense did the rest, forcing Kaepernick into three fourth-quarter turnovers, as the Seahawks remained close to invincible at noisy-beyond-belief CenturyLink Field.

Following a disappointing 3-13 season for the Redskins, the Post Sports Live crew debates what are reasonable expectations for Jay Gruden's first year as head coach. (Post Sports Live/The Washington Post)

“They’re really excited about this, this accomplishment . . . but they know we’re not done,” Seahawks Coach Pete Carroll said of his players after Sherman celebrated the final interception by being penalized for taunting and jumping into the stands.

The Seahawks will face the Denver Broncos on Feb. 2 in the NFL’s first New York-area Super Bowl. The game will match a Denver offense ranked first in the league during the regular season against Seattle’s top-ranked defense. The Seahawks lost their previous Super Bowl appearance eight years ago to the Pittsburgh Steelers.

The 49ers forced a turnover by Wilson on the game’s first play from scrimmage and led 10-0 after a second-quarter touchdown run by tailback Anthony Dixon. They led 17-10 after Kaepernick’s third-quarter touchdown pass to wide receiver Anquan Boldin. But the 49ers unraveled from there, and the Seahawks scored the game’s final 13 points.

“The ball thrown to Crab, that really could have gone either way,” said 49ers Coach Jim Harbaugh. “If that goes about an inch or two, Crabtree catches it for a touchdown and we win. But Richard Sherman made a terrific play.”

Harbaugh’s team was playing in its third straight NFC title game but failed to reach a second Super Bowl in a row.

“It was a 15-round fight right down to the last. . . . Just one drive, one touchdown drive, and we move on,” Harbaugh said.

The 49ers led early. Outside linebacker Aldon Smith stripped the ball from Wilson’s hand on the Seahawks’ opening offensive play and fell on the fumble. The 49ers took over at the Seattle 15-yard line but managed only a field goal. The Seahawks’ first three possessions resulted in the opening-play turnover and two punts.

Kaepernick was a virtual one-man show on offense early on, reaching 100 rushing yards by early in the second quarter. He weaved his way around Seahawks defenders for a 58-yard scramble that set up Dixon’s one-yard touchdown dive on a fourth-down play.

Wilson finally got the Seahawks going with some improvisation, moving around to buy time before finding Baldwin behind the San Francisco secondary for a 51-yard completion. But the Seattle drive stalled from there, and the Seahawks were left settling for Hauschka’s first field goal.

The Seahawks got even in the third quarter when Lynch, after being limited to 33 first-half rushing yards, rumbled for a 40-yard touchdown. But the 49ers had an immediate response with Kaepernick’s 26-yard touchdown pass to Boldin. Baldwin’s 69-yard return on the ensuing kickoff set up another Hauschka field goal for the Seahawks as the points suddenly began accumulating rapidly.

Seattle grabbed its first lead on Wilson’s 35-yard touchdown pass to Kearse. It came amid confusion on a fourth-and-seven play. The Seahawks first sent Hauschka on the field for what would have been a 53-yard field goal try. But the Seahawks called a timeout, then sent the offense back on the field.

Kaepernick lost a fumble on a sack by Seahawks defensive end Cliff Avril. Seattle took possession at the San Francisco 6-yard line but couldn’t score as Wilson and Lynch botched an attempted handoff on fourth down from the 1. The 49ers appeared to have recovered a fumble on a third-down play on which linebacker NaVorro Bowman was hurt when his left leg was caught beneath a pile of players, but the officials ruled the Seahawks had retained possession. Harbaugh said after the game the 49ers believed Bowman had suffered an injury to his anterior cruciate ligament.

The 49ers gave the ball right back to the Seahawks. Kaepernick had a pass intercepted by safety Kam Chancellor, leading to Hauschka’s third field goal.

“I think this was a game that we all expected, two great defenses going at it,” Seahawks safety Earl Thomas said.