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.

Rookie 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.

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.

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.

Brady shook off a poor first half that included two interceptions and completed 19 of 30 passes 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. 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.

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 the 4-yard touchdown. He later 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.

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 was also 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.

NOTES: The Colts lost TE Dwayne Allen to a sprained ankle in the first half. … Colts starting DT Arthur Jones (ankle) was inactive and missed his seventh game. … Other Indianapolis inactives were LBs Henoc Muamba and Victor Butler, OL Lance Louis, Khaled Holmes and Xavier Nixon and DT Kelcy Quarles. … Patriots inactives included the team’s sack leader, DE Chandler Jones (hip). Zach Moore started in his place. … Other New England inactives were WR Aaron Dobson, RB James White, S Don Dones, CB Alfonzo Dennard, T Jordon Devey, DE Chandler Jones and DL Casey Walker. … Adm. James A. Winnefeld Jr., vice chairman of the joint chiefs of staff, participated in the pregame ceremony.