GREENVILLE, S.C. — Grayson Allen has embraced his role as Duke’s sixth man over the past three weeks.

“It just to give the team that extra boost,” he said.

“And score points,” Blue Devils coach Mike Krzyzewski interjected.

Allen did both to keep second-seeded Duke’s postseason perfect in an 87-65 victory over Troy in the NCAA Tournament on Friday night to start the East Region.

Allen had 21 points off 5 of Duke’s 13 3-pointers and Jayson Tatum added 18 points and 12 rebounds.

“I’m coming in with fresh legs off the bench,” Allen said. “I’m coming in to explode, really.”

Shrugging off the chorus of bad-boy boos each time he touched the ball, Allen helped the Blue Devils (29-7) improve to 34-7 all-time in opening NCAA games. They’ll face either No. 7 seed South Carolina or No. 10 seed Marquette and its coach, former Blue Devils point guard and assistant Steve Wojciechowski, on Sunday.

Jordon Varnado had 18 points to lead Troy, which made its first NCAA appearance since 2003. Varnado said the players came out sluggish and could not fight their way out of it. “We’ve got to use this motivation and fire we had before the game to come back hard” next year, the sophomore said.

Duke, which averaged eight 3-pointers a game this season, hit 10 in the opening half to quickly pull away from the Trojans. Tatum opened the game with a 3. A short time later, Frank Jackson, Luke Kennard and Matt Jones had long-range baskets on consecutive possessions as the Blue Devils jumped to a 16-4 lead less than 5 minutes in.

The lead shrunk to 9 points in the second half, the final time at 59-50 on Wesley Person Jr.’s basket with 14:32 to go. But Jones and Allen followed with 3s and the Trojans (22-15) could not rally.

Duke finished with 13 3-pointers, its highest total in nine games since hitting the same amount in a win over Wake Forest on Feb. 18.

S. California 66, SMU 65:

TULSA, Okla. — Elijah Stewart hit a late 3-pointer for No. 11 seed Southern California as the Trojans upset sixth seeded SMU in the first round of the NCAA Tournament.

SMU’s Shake Milton missed a floater at the buzzer.

Stewart had 22 points for the Trojans (26-9). Bennie Boatright and Chimezie Metu each added 14 for USC, which advances to play Baylor in the second round of the East region on Sunday.

USC also rallied from a big deficit in the second half in its First Four win over Providence.

Semi Ojeleye had 24 points and 10 rebounds and Sterling Brown had 17 points for SMU (30-5), which had won 16 straight.

SMU was in the NCAA Tournament after being banned from postseason play a year ago for multiple violations, including academic fraud and unethical conduct.

S. Carolina 93, Marquette 73:

GREENVILLE, S.C. — Sindarius Thornwell had 29 points and 11 rebounds to help seventh-seeded South Carolina win its first NCAA Tournament game in 44 years.

If the Gamecocks (23-10) want an NCAA winning streak, they will have to beat No. 2 seed Duke.

Marquette (19-13) gave fans some serious worries in the opening half, going up by 10 points. But the Gamecocks used an 11-0 run midway through the second half to take control. When Thornwell, voted Southeastern Conference player of the year by league coaches, nailed his third 3-pointer with 6:37 to play, South Carolina was up 76-67 and pulling away.

P.J. Dozier had 21 points, 13 in the South Carolina’s second-half rally.

Jujuan Johnson had 16 points to lead Marquette.

Baylor 91, New Mexico St. 73:

TULSA, Okla. — Al Freeman came off the bench to score 21 points, and No. 3 seed Baylor defeated No. 14 seed New Mexico State 91-73 in the first round of the NCAA’s East Regional.

Jo Lual-Acuil scored 16 points and Johnathan Motley added 15 points and 10 rebounds for the Bears (26-7), who were upset in the first round by Georgia State and Yale the previous two years.

Ian Baker and Braxton Huggins each scored 19 points for New Mexico State (28-6).

Huggins hit a 3-pointer at the buzzer to give New Mexico State a 40-38 lead at the half. The Aggies made 6 of 14 3-pointers before the break to counter Baylor’s 55 percent shooting.