Blount Force

The shootout between Tom Brady and Andrew Luck in Saturday night’s divisional playoff game was a riveting duel for three quarters. It had everything a postseason game should have, with Luck cast as the resolute heir apparent who played brilliantly as he tried to knock off Brady, the Patriots longtime king of playoff excellence.

But, ultimately, it was not a fair match. Brady had a secret weapon in the New England huddle in this struggle against the Indianapolis Colts: the fourth-year running back LeGarrette Blount.

Early in the fourth quarter with the Patriots ahead by just a touchdown, Blount broke open a tense game with a 73-yard dash into the end zone. It was Blount’s fourth touchdown of the game, a Patriots record. Two plays later, Luck cracked, finally looking like the 24-year-old second-year player he is.

Luck heaved a pass into double coverage and it was easily intercepted. Five plays later, the Patriots had scored again and were leading by 21 points.

There was no miracle Luck comeback this week. The Patriots will be going to their third consecutive A.F.C. championship game next weekend. It will be the eighth conference championship in the Brady era.

The Patriots and Brady, their 36-year-old quarterback, eliminated Indianapolis once again in the postseason, holding off the upstart Colts, 43-22.

“People have counted us out throughout the season,” Brady said, “but I think we have a locker room full of believers. When you keep playing at this time of the year, each game gets bigger. And after tomorrow, there will only be four teams left, and it feels good to be one of them.”

The doughty Patriots, who have lost six starters to injury this season including Brady’s favorite target, tight end Rob Gronkowski, continue to find ways to play in the most meaningful January games. Next Sunday, New England will play the winner of Sunday’s Denver Broncos-San Diego Chargers game for the A.F.C. berth in the Super Bowl.

Against the Colts on Saturday, the Patriots had to be resourceful in new and unexpected ways. Their punter, Ryan Allen, injured his shoulder after a botched second-quarter snap, which meant that place-kicker Stephen Gostkowski had to take over Allen’s duties — even though Gostkowski almost never practices punting.

Gostkowski averaged 41.8 yards on five punts, repeatedly keeping the Colts from gaining good field position.

“I just got lucky; I’m not going to lie,” Gostkowski said.

Allen’s absence also meant that Brady had to hold on the Patriots’ extra-point attempts.

“I never practice that,” Brady said with a laugh. Asked the last time he held on a place-kick, Brady said: “I think in the Orange Bowl 14 or 15 years ago. Maybe I’ll renegotiate my contract since I have all these new responsibilities.”

It was a jovial Patriots locker room afterward, which was in juxtaposition to the mood inside Gillette Stadium as the fourth quarter began Saturday. Luck’s athleticism and pluck had kept the Colts in the game. While the Patriots never trailed, Luck’s star turn had the home crowd uneasy, especially with the New England lead down to 7 points.

But the Patriots had been wearing down the Colts with their running attack since the earliest moments of the game. Patriots Coach Bill Belichick said the game plan had not been to overemphasize the running game, but he added, “We had some success with it so we stayed with it.”

The result was 234 rushing yards and six rushing touchdowns, a Patriots’ single-game record. Blount, undrafted when he came out of college in 2010, rushed for 166 yards on 24 attempts. His four rushing touchdowns were the second most in a N.F.L. playoff game. San Francisco’s Ricky Watters ran for five touchdowns in the playoffs after the 1993 season.

“Tom Brady has won more of these games in the postseason than anybody,” Blount said. “I was just trying to help out.”

The Patriots punishing ground game — Stevan Ridley had 52 rushing yards and two touchdowns as well — seemed to leave the Colts defensive front line weary. When Blount took a handoff and sliced toward the middle of the line on the Patriots first play of the fourth quarter, a gaping hole appeared. Blount exploded through it and ran untouched for the decisive score of the game.

“I’m just glad they had confidence in me to keep giving me the football,” said Blount, who is in his first year with New England and was playing in his first playoff game. “On this team, I try to keep my eyes open because there are a lot of veterans who calmly deliver in big games.”

Performing under that kind of pressure is a skill the Colts are trying to develop. They lost their only playoff game last season — Luck’s rookie year — but were 1-1 this year, including a 28-point comeback victory over the Kansas City Chiefs in the playoff’s opening round.

Luck, who threw for 331 yards by completing 20 of 41 passes Saturday, has clearly elevated his game. Although he threw an interception on his second pass and struggled in the final quarter, he still exhibited all the attributes of a budding star — even in a game played in a steady rain.

Luck’s first interception led to a 7-0 New England lead, and then, after another inept Colts drive, Brady had the Patriots up, 14-0. But Luck has already proven in this postseason that he is not easily discouraged. With two passes to tight end Coby Fleener and two productive runs from Donald Brown, Luck soon had Indianapolis on the New England 38-yard line.

Luck turned and looked for wide receiver LaVon Brazill streaking down the right sideline. A perfect pass fell in Brazill’s hands and the Patriots lead was cut in half.

It was not 14-7 for long. Brady was still hot and this time he led the Patriots 75 yards on 14 methodical plays, a drive that ended with Blount’s third 2-yard touchdown run.

But Luck was undeterred, rallying the Colts for a field goal. A poor snap on a punt led to an Indianapolis safety to reduce the Patriots lead to 21-12 at the half.

The Colts scored first in the third quarter with a field goal and then traded touchdowns with the Patriots to bring the score to 29-22. It was beginning to look as if Luck and Brady would go head-to-head throughout the fourth quarter.

But a strong running game is essential in games played in the Northeast at this time of the year. The Colts rushed for only 69 yards, averaging 3.3 yards per carry. New England averaged 5.1 yards per carry.

And no run was bigger than Blount’s fourth-quarter, 73-yard scamper when the Patriots needed it most.

“It was a routine play where you bang it up in there,” Blount said. “But this time, the line made this huge hole and I knew nobody was going to catch me.

“It just seems like this team knows how to win games at this time of the year.”