DURHAM — Mike Krzyzewski was worried. His team had been undefeated and ranked No. 1 before losing one of its senior starters and its first game during the past nine days. He began to wonder, he later admitted, if his Blue Devils would make the NCAA tournament.

The first half of the game following the loss at N.C. State did little to reassure him, as Duke, still missing Ryan Kelly, trailed Georgia Tech by one after 20 minutes. His star, Mason Plumlee, was struggling, going just 2-12 from the field. But as the second half progressed, the coach felt much better.

It took Plumlee just two minutes to equal his field goal total from the first 20. A few possessions later, Plumlee received the ball on the low block and posted up Marcus Georges-Hunt. A dribble, pump fake and pivot later, Plumlee slammed the ball home, giving Duke a 10-point lead and forcing a Georgia Tech timeout. As Plumlee ran toward the sideline, Krzyzewski ran toward him on the floor.

Krzyzewski jumped up and threw his arms around the 6-foot-10 forward’s shoulders. It was the type of celebration the Blue Devils had previously seen only on film.

“I give emotion a lot during my 33 years here at Duke, so I am going to do whatever I think my team needs,” Krzyzewski said. “I did that in 1980, and I should do it in 2013, so I thought that’s what my team needed. It’s what I gave.”

Plumlee is the type of player who can bring this kind of emotion out of Krzyzewski, who says the senior is a veteran completely dedicated to making himself and the team better, and a rarity in college basketball today. Plumlee’s drive and focus reminds the coach of Christian Laettner, and of professionals like LeBron James, who Krzyzewski coached on the U.S. Olympic team.

Plumlee constantly reaches out to Krzyzewski, whether initiating conversation in the locker room or going over the daily practice plan before the rest of the team hits the floor. That’s a role he has grown into, he said.

“I was more comfortable knowing that I felt like I was the guy this year,” Plumlee said. “That’s a role that I’ve always wanted here, and now that I’ve had it, I love being in that role.”

Because of that, player and coach have grown quite close.

“He’s a really good guy,” Krzyzewski said. “Like, I love him. He and I have an amazingly strong bond. I like that, too, because as I get older, the age difference keeps expanding. They don’t get older. They’re in that same zone. Those are the things I’ve loved the most out of my time. To know that I can have that level with a kid, that helps.

“Most of the time in coaching, you give and you don’t get as much. And when you have a player who gives to you, boy, that’s terrific.”

Unquestioned leader

Plumlee was ranked the 10th best prospect in the Class of 2009 by ESPN. Only one other top-10 player from that year (Florida’s Kenny Boynton) is still in school.

Before arriving at Duke, Plumlee thought he could be a one-and-done guy like Kentucky’s John Wall of Raleigh and DeMarcus Cousins or Kansas’s Xavier Henry. But maybe he’d stay for two years, he thought after experiencing the game at the college level. Maybe even three.

After his junior year, Plumlee was projected by most as a late first-round pick (his older brother Miles was picked 26th overall by the Indiana Pacers in the 2012 NBA draft) . He discussed his decision with his family, former Duke teammate Jon Scheyer, and the Blue Devils’ coaching staff. As Krzyzewski talked with Plumlee, he became convinced he was coming back.

“He’s been a little bit of a dreamer in a good way,” Krzyzewski said. “He was frustrated with himself that he had not achieved what he dreamed about by the end of his junior year.”

Plumlee now says he knew at the end of last season he needed to return to Duke. And he realized during meetings with the coaching staff that he would have the opportunity to be the unquestioned leader of this year’s team.

Krzyzewski began to see a change in Plumlee. He had seemingly matured overnight, and he had a clear vision for his senior year. It was more than a dream – he had a plan outlining the commitment he would have to make.

“I knew just from talking to Coach last spring the position he was going to put me in,” Plumlee said. “I knew individually I would have a great season. It was just about making sure we have a great season.”

And Plumlee has done his part to make sure that would happen. Heading into Tuesday’s game he was averaging 17.1 points and 10.3 rebounds per game. During the summer, he exchanged calls with Krzyzewski while he was in London, keeping the coach informed of the team’s work in Durham. During the season, he has learned the pregame scouting reports for every position on the floor to help make sure his teammates understand their roles.

“The biggest thing is that I’m responsible for more than just myself now,” Plumlee said. “I’m talking about the game plan more, and then I’m more invested in it when I’m helping other guys.”

Preparation is a habit Krzyzewski and his staff tries to instill in all Duke players, and that’s nothing new.

“If you don’t prepare well, then you’re setting yourself up to fail,” said former Duke great Carlos Boozer. “But if you prepare, you’re giving yourself a chance to win. That’s the big deal.”

Plumlee’s preparations for this season began well before the start of practice. He did something he hadn’t done previously, showing Krzyzewski a written list of his goals for the season. They became “our goals,” shared by Plumlee, Krzyzewski and the rest of the team.

Plumlee remembers them well.

“Absolutely,” he said with a smile.

But he’s not ready to reveal them.

“Well, there’s a lot left to be determined,” he said. “I will say that I haven’t accomplished any of them yet.”

It takes a senior

Nearly a month after Plumlee invigorated his coach and team with his two-handed slam against Georgia Tech, he found himself in a more critical position. Duke had lost the lead at Boston College and trailed by five with two minutes to go. A 3-pointer from Quinn Cook made it a one-possession game. And, with Duke down two, Plumlee, a 61.3 percent free throw shooter, went to the line.

“They picked the weakness,” Krzyzewski said.

He hit both shots. One possession later, he hit one more, giving Duke the 62-61 lead that held up at the final horn.

Plumlee had started slow against the Eagles but finished with 19 points and 11 rebounds.

“At different times in games, whether he has started slowly or not played as well, Mason has been so mature that if you tell him, ‘look man, you’re not playing well,’ he will step forward in front of the team and say ’I got it, I’ll play better,’“ said assistant coach Steve Wojciechowski. “And he has. Those are cool moments to be a part of in the locker room.”

Could an underclassman ever lead like Plumlee?

“I don’t know about a young guy,” Krzyzewski said. “One of the things that makes a great senior leader is that he has got the gift of experience, of going through highs and lows.”

Another legendary senior Duke leader, Shane Battier, has his doubts as well.

“Duke has historically been an upperclassmen’s program, you wait until your time comes to take the reins and lead,” Battier said. “Out of necessity you’ll see younger leaders, but it will take an incredible amount of maturity for a freshmen or sophomore to lead like a junior or senior. You don’t have the experience.”

Connecting to Krzyzewski

Battier, like Plumlee, needed time to develop his relationship with Krzyzewski.

“He’s a complex man,” Battier said. “After being around him for three years, you finally get insight into what makes him go and what makes him tick.”

Over the years, Battier learned that Krzyzewski had a great sense of humor. “And that shocks most people,” he said.

“I’ll never forget, after we won the (NCAA) Regional in 1999, for whatever reason Saturday Night Fever was playing on the bus. And Coach starts doing the John Travolta walk up and down the aisle.

“Here’s a guy who is so fiery and passionate on the sideline doing the John Travolta walk. He’s the best,” Battier said as he laughed. “He’s the greatest coach ever, but at the end of the day, he can laugh. He’s human.”

Krzyzewski showed a glimpse of that this year, back when he bear-hugged Plumlee during the game against Georgia Tech. Krzyzewski, Wojciechowski, Chris Collins, Jeff Capel and Nate James, all the assistants, have grown closer to Plumlee this year.

And all of those relationships began to deepen last spring, as Plumlee and Krzyzewski started to imagine his senior year.

“I think just coming back and showing that I want to play for him, I appreciate what he does for me as a player,” Plumlee said of Krzyzewski. “A lot of kids could have left. Even though I wasn’t projected to go extremely high, it’s easy to leave. But I know what he does. It’s turned out for the best, I think.

I keep saying there’s a lot of basketball left to be played, but I’m so happy that we made the decision that we did.”

Krzyzewski is, too, every day before practice, when he talks with his senior star.

Keeley: 919-829-4556; Twitter @laurakeeley