BLOOMINGTON, Ind. -- Duke coach Mike Krzyzewski could not say enough about his team's determination.

"We're exhausted. They have such a will to win," Krzyzewski said after top-ranked Blue Devils pulled away from Indiana for a 91-81 victory in the Big Ten/ACC Challenge on Wednesday night. "This is our ninth game in 20 days, and 10 of those days we've been on the road.

"They're dead right now, but they played those last five minutes with an incredible will to win. I got a special group."

Marvin Bagley III, one of four freshman starters, led Duke (9-0) with 23 points on 10-of-15 shooting, and he grabbed 10 rebounds. Senior Grayson Allen added 21 points for Duke, hitting 7 of 12 shots and all five free throws. Duke forward Wendell Carter Jr. fouled out late with 18 points, on 7-of-9 shooting, and 12 rebounds.

After Indiana reduced its deficit to 78-77 with 4:11 to go, the Blue Devils finished the game with a 13-4 spurt.

"We executed really well at the end," Krzyzewski said.

The game was tied 17 times, and there were 16 lead changes. Indiana's largest lead was four points.

"Give Duke credit," Hoosiers coach Archie Miller said. "They've been in some hostile games here in the last two weeks, and they've been able to come through."

Robert Johnson was the top scorer for the Hoosiers (4-3) with 17 points before fouling out with 28 seconds left.

Duke hit 33 of 60 shots (55 percent) while Indiana was 30 of 59 (50.8 percent) from the field. However, both teams shot poorly from beyond the 3-point line. Duke was 3 of 17 (17.6 percent) and Indiana was 5 of 21 (23.8 percent).

A three-point play by Carter gave Duke a 78-75 lead with 4:32 to go. Following a pair of free throws by De'Ron Davis to slice the lead to 78-77, Allen sank a 3-pointer to give the Blue Devils an 81-77 advantage.

"Grayson's 3 was the biggest shot of the game, I thought," Krzyzewski said.

Davis, who scored 16 points, was 6 of 7 from the field but made just 4 of 9 from the free-throw line.

"He's a big weapon for us," Johnson said of Davis. "Whenever we feel he has an advantage inside, he has to get the ball."

Juwan Morgan added 14 points for the Hoosiers.

Indiana was 16 of 26 from the free-throw line while Duke was 22 of 29.

"Free-throw line is disappointing," Miller said. "As a team you have to be better than that to win games like that."

The Blue Devils, who led 42-38 at halftime, took a 52-42 lead before the Hoosiers rallied with a 15-5 spurt to tie it at 57-all on a 3-pointer by Collin Hartman.

The Hoosiers took a 61-59 lead on two free throws by Hartman (11 points).

Johnson hit a layup to push Indiana's advantage to 63-59 with 11:48 to go. The lead went back and forth over the next several minutes.

The Blue Devils sank 18 of 33 shots (54.5 percent) to take a four-point lead at halftime. The Hoosiers made 16 of 35 shots (45.7 percent) to stay close.

"You can see from watching their tapes that they are getting better every game," Krzyzewski said. "I thought they played really well. They shared the ball and were a tough team to defend for us."

NOTES: Duke has won four in a row against Indiana and leads the overall series 6-3, including 2-0 in Bloomington. ... Duke is 17-2 in the 18-year history of the Big Ten/ACC Challenge. Indiana is 7-10. ... F Marvin Bagley III became the first player in Duke history to have back-to-back 30-point, 15-rebound games when he did it in the PK80 Invitational in Portland, Ore. Bagley entered Wednesday's game tied for the NCAA lead with six double-doubles in the first eight games. He got his seventh Wednesday night... Indiana F Collin Hartman played in his second game of the season after missing the first five game with a groin injury. Hartman missed all of last season with a knee injury.