PORTLAND, Ore. -- After receiving a wake-up call in the first half, the No. 1 Duke Blue Devils began the Phil Knight 80 Invitational with a 99-81 first-round victory over the upstart Portland State Vikings on Thursday.

"I thought Portland State played amazingly hard and well -- they knocked us back," Duke coach Mike Krzyzewski said. "They're well-coached... we beat a really good team today."

The Blue Devils (5-0) went into the half trailing 49-45 but came out much more disciplined in the second half to slow the game down.

Potential No. 1 overall NBA pick Marvin Bagley III led Duke with 18 points and 15 rebounds. Trevon Duval added 22 points and Wendell Carter, Jr. had 16 points and 10 rebounds.

"Going into the second half, we had to wake up," Bagley III said. "We just had to come out play better, it's as simple as that -- we started to feel the energy start to change and we ran with it."

Deontae North scored 24 points for Portland State (4-1).

Eventually, Duke's switch to a 2-3 zone and size wore down Portland State in the second half. Bagley was nearly unstoppable down low as no Vikings player came close to his combination of size and length.

"In the second half, they had to react to us," Krzyzewski said. "In our '12' or zone defense, we were much more active and there wasn't the breakdown."

Bagley's ability to create room in tight spots and see over the smaller Portland State players was invaluable to slowing the game down.

Altogether, the Blue Devils dominated the Vikings in the paint, outscoring them 54-26, including a 49-37 rebounding advantage.

"Their size was really a tough deal for us," Portland State coach Barret Peery said. "Those balls that even when they missed shots around the rim, we had four or five guys around the rim and they were able to keep balls alive with their size and keep it on the glass."

The Vikings were able to stay in the game with their three-point shooting. They knocked down 12 in the game, outscoring the Blue Devils 36-12 from beyond the arc.

Portland State came out of the gate like a team with nothing to lose.

North led the charge with 20 points in the first half, hitting 4 of 5 from beyond the arc. He picked apart the Blue Devils with a solid outside jumper combined with the skills and athleticism to score down low.

North fouled out midway through the second half. Bryce Canda added 14 points, 10 rebounds and five assists. Portland State committed 33 fouls, compared with just 16 fouls by Duke.

"It was kind of a crazy game with all the physicality," Krzyzewski said.

Grayson Allen, one of five Blue Devils in double figures, chipped in 14 points and nine assists.

Duke advances to play Texas on Friday. Portland State will face Butler.

NOTES: F Marvin Bagley III was the No. 1 recruit in the class of 2017. ... Duke started four freshmen (Bagley III, G Trevon Duval, F Wendell Carter Jr. and G Gary Trent Jr.). ... Deontae North's 20 points in the first half were the most he has scored in a Portland State game since posting 25 against Cal State Bakersfield early last year. ... North was thrown out of the game for picking up two technical fouls in the second half ... Duke made 31 of 42 free throws. ... There were four technical fouls in the game. ... Five Portland State players fouled out.