Kelly scored 15 of his 18 points in the decisive first half and Plumlee added a double-double in Duke's 88-50 rout of Delaware on Saturday.
Plumlee had 18 points and 11 rebounds for the Blue Devils (8-0), who never trailed, shot 52 percent and led by 46.
"If playing hard is our habit," Plumlee said, "we'll be a good team and keep getting better."
Seth Curry, the other scholarship senior on the roster, missed the first game of his career at Duke with an injured ankle. Against the struggling Blue Hens (2-6), the Blue Devils certainly didn't need him.
"When a guy like that is out ... it's everybody's responsibility to step up," redshirt freshman Alex Murphy said.
Devon Saddler had 23 points for Delaware, which was beaten soundly by the highest ranked opponent it had ever faced. Saddler was 8 of 22 and took more than one-third of his team's shots.
"We have tried to put ourselves in position to play some `up' games, to play the best competition possible," Blue Hens coach Monte Ross said. "When you do that, there is always a possibility that you are going to lose some of those games."
They announced about an hour before the game that Curry wouldn't dress because he injured his left ankle on Wednesday night in the second half of the win over No. 4 Ohio State, ending a streak of 78 consecutive games for the senior sharpshooter.
The last time the Blue Devils played without Curry, they won a national championship -- beating Butler in the 2010 title game while he sat out as a transfer from Liberty.
Wednesday's tense 73-68 win over the Buckeyes was Duke's second straight victory against a top-five opponent and its third of the season, along with wins over then-No. 3 Kentucky and then-No. 2 Louisville, making the Blue Devils the first team since 2001 Ball State to beat consecutive top-five foes.
This one was nowhere near as stressful for the Blue Devils, who extended their NCAA-best winning home streak against non-conference opponents to 98 and improved to 24-0 under Mike Krzyzewski against CAA teams.
"You know, sometimes in these situations ... there's a chance for a letdown, and we didn't have it," Krzyzewski said. "Our guys played hard and well the whole way."
Duke reeled off 15 straight points early while Delaware missed 11 consecutive shots, went up by double figures to stay before the first time out and spent the rest of the first half methodically growing its lead.
Kelly capped a 25-7 spurt with a baseline drive with 7 1/2 minutes before the break that gave Duke its first 20-point lead at 29-9, and his 3-pointer with about 40 seconds left in the half made it 42-16.
"When I get opportunities, I have to take advantage of them," Kelly said. "I think early in my career, I was a little bit one-dimensional. I was just being a shooter, and now I'm just trying to be a player -- whether that (means) taking open shots or making plays for myself and others."
The Blue Hens entered this season winless against current Atlantic Coast Conference teams since 1962 before beating Virginia on Nov. 13 to reach the semifinals of the NIT Season Tip-Off -- and they haven't won a game against anyone since.
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Maryland point guard Melo Trimble, considered a lock to leave the program before struggling in the second half last season, has withdrawn from the NBA draft and will return for his junior season.
Louisville's Chinanu Onuaku, who recently underwent a medical procedure to correct a heart rhythm issue detected during the combine, will keep his name in the NBA draft pool.
Andrew White III will return to the Nebraska men's basketball team next season after removing his name from the NBA draft.