INDIANAPOLIS — The unlikeliest of heroes emerged for New England on Sunday night, giving the Patriots a firm grasp on the top spot in the AFC.

First-year running back Jonas Gray set a franchise record with four rushing touchdowns and more than doubled his career totals with 38 carries for 199 yards, and the Patriots continued their dominance of the Andrew Luck-led Indianapolis Colts, winning 42-20 in Lucas Oil Stadium.

“They hammered into us all week the keys to winning the game, and one of them was getting the running game going,” Gray said. “We were able to do that early and often, and the guys did a good job of blocking up front.”

Gray, an undrafted free agent from Notre Dame who entered the game with 131 yards on 32 attempts in three career games, scored twice in each half. His 2-yard plunge in the third quarter gave the Patriots a 28-13 lead, and his 1-yard surge in the fourth made it 35-20.

After the Colts failed on a fourth-and-10 try on their next possession, New England quarterback Tom Brady hit tight end Rob Gronkowski for a 26-yard touchdown with 6:46 remaining that sealed it.

“A lot of the things the Colts were able to do here this year, fortunately they weren’t able to do tonight,” Patriots coach Bill Belichick said.

With their sixth win in a row, the Patriots (8-2) moved two games ahead of the Miami Dolphins in the AFC East and took a one-game lead over Denver atop the conference after the Broncos lost to the St. Louis Rams. The Colts fell to 6-4, one game ahead of the Houston Texans in the AFC South.

In Luck’s three games against the Patriots, the Colts have been outscored 144-66.

“What matters is we lost a game, we’ve got to fix what we did wrong and go out and try and win our next one because that’s the biggest one now,” Luck said. “Thankfully this is not the last game of the season. We’d truly be sick to our stomachs, very sick to our stomachs. We’ve got a lot to improve.”

Brady shook off a poor first half that included two interceptions, finishing 19 of 30 for 257 yards and two touchdowns.

Luck extended his streak of 300-yard games to eight by completing 23 of 39 for 303 yards and two scores, including one to tackle Anthony Castonzo early in the fourth quarter that cut the deficit to 28-20. Tight end Coby Fleener had seven receptions for a career-high 144 yards. However, the Colts managed just 19 rushing yards on 17 attempts, compared to the Patriots’ 244 yards on 45 carries.

“Yeah, they forced us to be one-dimensional,” Luck said. “It’s tough sledding. We know that going into the game. We just couldn’t keep it close enough to have a fighting chance at the end.”

While the star quarterbacks both struggled in the first half, Gray was dominant, racking up 100 yards on 14 carries and scoring the first two touchdowns of his career — and the first rushing scores for the Patriots since Week 5.

Gray carried four times for 34 yards on the Patriots’ opening scoring drive, including a 4-yard touchdown. He added a 2-yard score that put the visitors ahead 14-3 with 3:50 remaining in the first half.

While Gray had his way, Brady struggled mightily, throwing two interceptions to Colts safety Mike Adams and completing just 10 of 19 attempts for 84 yards before the break.

The Colts couldn’t capitalize on the first pick, but the second — a terribly underthrown, back-foot lob toward Gronkowski — gave the home team field position at the New England 23 late in the half. Three plays later, Luck found wide receiver Hakeem Nicks in the corner of the end zone for a touchdown that cut the margin to 14-10 at the half.

Luck also was picked off on a tipped ball intended for wide receiver Reggie Wayne, with safety Devin McCourty snagging the ball after a deflection by cornerback Darrelle Revis. The Patriots then drove 68 yards for their second touchdown.

What the Patriots said:

“I had an indication all week that I was going to be a big part of the game plan. We knew that getting back to the run game was going to be a big emphasis. It’s kind of funny because on Saturday I remember walking into the building, and Mr. (Robert) Kraft pulled me aside and said ‘You’re going to have a big game this week, so be ready.’ Just hearing that from the owner, hearing that from the head coach, hearing that from the leaders of the team definitely gives you a positive outlook. It definitely gives you the mindset to go out and do your best.” — Running back Jonas Gray, who ran for four touchdowns and 199 yards.

What the Colts said:

“We have to get better. We have to get better stopping the run. Not just our front seven, everybody. All 11 players, we got to swarm to the ball. We can’t let teams do that to us, we just can’t.” — Safety Mike Adams, after the Patriots ran for 244 yards against the Colts.

What we learned about the Patriots:

1. A month after Stevan Ridley landed on injured reserve, the Patriots found an impressive new lead back. Jonas Gray piled up 199 yards and four touchdowns on 38 carries as New England dominated the game on the ground. Two weeks earlier, in his second career NFL game, Gray gained 86 yards on 17 carries against the Chicago Bears. He figures to get plenty of action the rest of the season.

“He’s just a smart, hard-working kid,” coach Bill Belichick said. “He’s got good power. He runs hard. His game is what we saw tonight.”

2. The Patriots can win even when Tom Brady isn’t at his best. The veteran quarterback threw two first-half interceptions, and he finished a modest 19-for-30 for 257 yards. However, New England converted nine of 12 third downs, and Brady fired two second-half touchdown passes to help put the game away.

–DE Chandler Jones, the Patriots’ sack leader with 4.5, was inactive due to a hip injury. Zach Moore started in his place. Jones hasn’t played since Oct. 16.

–RB Jonas Gray set a franchise record with four rushing touchdowns and more than doubled his career totals with 38 carries for 199 yards. Gray, a first-year player who was an undrafted free agent from Notre Dame, entered the game with 131 yards on 32 attempts in three career games. He scored twice in each half.

–TE Rob Gronkowski scored a touchdown for a third consecutive game, grabbing a game-sealing, 26-yard pass from QB Tom Brady in the fourth quarter. Gronkowski finished the night with four receptions for 71 yards.

What we learned about the Colts:

1. Indianapolis’ middle-of-the-pack rushing offense needs improvement. The Colts managed just 19 yards on 17 carries, putting the entire burden on quarterback Andrew Luck’s arm. “When you get behind and they make you one-dimensional, it’s extremely difficult,” Indianapolis coach Chuck Pagano said. “We just couldn’t come up with any answers.”

2. The Colts’ defense is inconsistent. For the second time in three games, Indianapolis allowed its opponent to score at least 42 points. The Steelers rolled to a 51-34 win over the Colts on Oct. 26. On the flip side, four times this season, Indianapolis limited the opposition to 17 points or fewer.

“It was a horrible performance from the defense,” inside linebacker D’Qwell Jackson said of the effort against New England. “This one definitely stings, but I’m more than confident we’re going to come in tomorrow, watch it, grade it and do whatever we got to do to fix this problem because for us to get to where we want to go, we got to correct those things.”

–TE Dwayne Allen left the game due to a sprained ankle in the first half, and he will undergo an MRI exam. He did not have a pass thrown his way.

–RB Ahmad Bradshaw (lower leg) left the stadium in a boot and on crutches after gaining 4 yards on seven carries. He also caught four passes for 7 yards, giving him an average of 1 yard per touch. Bradshaw is due to undergo an MRI exam.

–TE Coby Fleener was the Colts’ biggest offensive threat Sunday. He finished with seven catches for 144 yards. He entered the game with 22 catches for 295 yards on the season.