KANSAS CITY, Mo. -- Duke had one big half from the field, another from the line -- and a big game from DeMarcus Nelson.
Together, they put the ninth-ranked Blue Devils into the finals of the CBE Classic.
Nelson scored a career-high 23 points, and the Blue Devils shot 74 percent from the floor in the first half of Monday night's 71-56 semifinal victory over Air Force.
"I'm very confident in my shot," said Nelson, who also led Duke with three steals. "We have five unselfish guys. My play might be to take the shot or to make the extra pass."
Freshman Lance Thomas added 15 points and Jon Scheyer, another freshman, finished with 12 for the Blue Devils (4-0), who will play No. 13 Marquette in Tuesday's title game after the Golden Eagles beat Texas Tech 87-72 in Monday's late semifinal.
Air Force (4-1) will play the Red Raiders for third place.
Duke shot 17-for-23 from the field in the first half, but the Blue Devils went cold after the break and didn't make a shot after Greg Paulus' 3-pointer with 5:45 left gave them a 59-47 lead.
They still finished the game at 61 percent (25-for-41), including a 7-for-13 night from 3-point range. Air Force, the nation's scoring defense leader last year at 54.7 points per game, had held its first four opponents this season to an average of 35 percent shooting.
"They played well," Duke coach Mike Krzyzewski said. "We played well. We were fortunate we won. They are going to make some noise this year, no question about it."
The Blue Devils led 38-24 at halftime but didn't score for almost three minutes to start the second half.
The Falcons twice closed the gap to seven points, the last time on Dan Nwaelele's basket with eight minutes left that cut the deficit to 54-47, but went scoreless for nearly five minutes after that.
Jacob Burtschi missed a layup that would have made it 54-49 with 7:20 left, and Nelson made a layup on Duke's next possession.
Paulus followed with his 3-pointer, closing out the Blue Devils' scoring from the field and pushing the margin back to 12 points. The Falcons didn't get within double digits again.
"It was a great pass, and I flat-out missed it," Burtschi said. "That was a confidence-killer."
Burtschi and Nick Welch led Air Force with 12 points each, and Nwaelele added 10.
The Blue Devils didn't shoot a free throw in the first half but were 14-for-17 from the line in the second.
Duke opened the game on a 12-for-14 tear and held Air Force, which won its first four games by an average of 27 points, without a field goal for 6:45 in the first half.
Duke went on a 10-2 run and took a 36-20 lead with that spurt, which ended when Burtschi hit a layup with just more than 1½ minutes left before halftime.
"Their efficient offense the first 15 minutes decided the basketball game," Air Force coach Jeff Bzdelik said. "We gave Duke a lot of easy baskets. We were a lot more disciplined offensively in the second half."
Five of Nelson's points came in a spectacular five-second burst earlier in the half, when he hit a 3-pointer and then stole the inbounds pass and dunked to give the Blue Devils a 12-4 lead.
The Blue Devils outrebounded the Falcons 30-10, including a 13-4 advantage in the first half. The margin was 21-8 on Duke's defensive end.
"They had 10 rebounds at the half on defense," Bzdelik said. "We had 10 for the whole game. We're undersized, but you've just got to get a rear end to block out."
Duke left reserve forward Jamal Boykin, who averages 1.3 points and four rebounds, at the team hotel with the flu and a migraine headache.
Tuesday night's championship game will be the six-year-old tournament's fifth and final title contest at Municipal Auditorium, which has hosted more Final Fours (nine) than any other building. The last two rounds move next year to the Sprint Center, now under construction in downtown Kansas City.
