KEMBA WALKER IS watching Boston Celtics teammates Marcus Smart and Jaylen Brown get up jump shots after practice, and he's asked about what drives him to be so vocally supportive.

A perplexed Walker takes a beat to answer.

"I'm really just being myself," he says. "I'm really just genuinely happy for guys and my teammates. I love when guys have success. I've had a lot of success in my career, and I want guys to have great success."

It's an obvious answer, but not one to be taken for granted. Last season the Celtics struggled to maintain cohesion, a problem that was -- fairly or not -- usually attributed to the leadership of Kyrie Irving, the man Walker replaced as Boston's star point guard.

On Wednesday, the Celtics welcome the Brooklyn Nets to Boston (Wednesday, 7 p.m. ET on ESPN) for what was supposed to be a reunion with Irving, who'll miss the trip with an injured shoulder. Still, as the two teams meet for the first time this season, the contrast in the tone set by the two point guards is telling.

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THAT CONTRAST IS encapsulated in a pair of moments -- one last season, and one this -- with striking similarities.

On a Saturday in January, the Celtics trailed the Orlando Magic by two points with 2.9 seconds left. Jayson Tatum curled to the corner, took an inbounds pass from Gordon Hayward and missed a game-tying shot.

Irving was furious. He had words for Celtics coach Brad Stevens in the huddle, then for Hayward on the court after the final buzzer had sounded. In his postgame interview in the locker room, he proceeded to take his latest round of veiled shots at the team's young players.

Ten months later, a different-looking Celtics team found itself in a similar position: 4.7 seconds left, with the ball, this time tied at home against the New York Knicks.

Tatum again curled to the baseline, and received the inbounds pass -- this time from Marcus Smart. The third-year forward rose and buried the jumper, putting Boston ahead with 1.3 seconds to go. It was Tatum's first career go-ahead basket in the final five seconds, and continued both Boston's hot start and the positive vibes that emanate from the team.

"Jayson had that opportunity to get that last shot, and he made it," Walker said. "What more can I want? He won, he made a last-second shot, it was an amazing game, and I'm just happy. I'm just happy for my teammate."

It was an early lesson in why Walker was so beloved elsewhere.

"Not surprised," former Hornets teammate Marvin Williams said, when asked about Boston's hot start. "Not even a little bit. He fits right in.

"His personality is so infectious, man. He's somebody that you want to be around. He's somebody that you always want to go play with."

Those feelings were not felt frequently in Boston last season. The Celtics entered the year as favorites to make the NBA Finals. They ended it with a demoralizing second-round playoff exit to the Bucks in five games, following an uneven regular season that saw Boston never live up to its preseason hype.

It would be unfair to say Irving was the cause of all of Boston's woes. Stevens had to distribute minutes, touches and shots among a number of overlapping guards and wings -- including Irving, Smart, Tatum, Brown, Hayward and pending free agents Marcus Morris and Terry Rozier. Returning from a devastating leg injury, Hayward never looked comfortable, and his immediate insertion into the starting lineup -- and subsequent removal -- caused friction. So, too, did the specter of Irving's free agency and the potential for an Anthony Davis trade -- both of which hung over the team like an anvil all season.

Individually, Irving had possibly his best season as a pro. He was a second-team All-NBA selection for the first time, and he was inside the top 20 in ESPN's real plus-minus and posted a positive defensive real plus-minus for the first time in his career.

A panel of seven executives asked recently whether Irving or Walker is the more talented player all chose Irving. However, six of those same seven executives said, if they had to choose to have one of them on their team, they'd rather have Walker.

Irving said last season he was trying to learn how to be a leader on the fly. His approach was to -- repeatedly -- administer public tough love to his teammates, something he'd routinely do while citing the influence LeBron James had on him during their time together in Cleveland.

Walker, though, has -- repeatedly -- said his goal is a very different one: to try to ensure everyone is happy.

"For me, it's just the nature of this sport, like a team sport," he said. "You don't want nobody to be unhappy. You want everybody to play with joy, play with freedom, and have fun."

DESPITE WALKER'S OWN stellar play, the Charlotte Hornets were never more than an NBA footnote during his eight years there. They made the playoffs just twice, with two first-round exits, and rarely played on national television.

Yet Walker never complained. He never took shots at his teammates or the organization. He talked openly about wanting to stay in Charlotte. He still has a home there. His mom still lives there. And he still is beloved within the organization, and by the fan base -- even after leaving as a free agent this summer.

"I told Kemba, I want what's best for him," former teammate Cody Zeller said. "They have a great, great franchise, a great opportunity to win there. It was great while he was here in Charlotte, but I think he made the right decision for what was best for him."

Walker openly wept when the Hornets honored him with a video tribute before his first game back in Charlotte on Nov. 7. Zeller wore shoes honoring Walker's work with Charlotte's "Big Brothers Big Sisters" program. And, from top to bottom, the Hornets unequivocally praised what Walker did during his time with the team.

"He'd have a great game, but just like [Tim] Duncan he'd always deflect the attention somewhere else," Hornets coach James Borrego said. "He never wanted the attention. He'd always deflect it to someone else who made a big defensive play or made the right pass. He never wanted more, never wanted more attention, wanted his teammates to be embraced for what they were doing, as well, and I think he understands what that does for a team, and at the end of the day, he's really selfless."

Jeremy Lamb knows that well. The Indiana Pacers guard played alongside Walker at the University of Connecticut, where he and Walker won an NCAA championship together in 2011, and then for the past four seasons with the Hornets.

In a game against the Detroit Pistons last December, Lamb was struggling. He had shot just 3-of-12 on the night, and missed a critical free throw that allowed Detroit to tie the game in the final 30 seconds.

But when the game was on the line, Walker -- who had 31 points -- trusted Lamb to take the final shot and fed him the ball. When Lamb hit the buzzer-beater, Walker and his teammates mobbed him, and Walker later was emphatic during Lamb's postgame interview about why he trusted Lamb to make the play.

"Of course!" he shouted. "That's my son! I raised him!"

To Lamb, that was just par for the course for Walker, given the years of support his teammate had shown him.

"I would just say that as great as he is on the court, he's just as great off the court," Lamb said. "In terms of just leadership and as a friend, he's always looking to make people better."

Walker demonstrated that again last week, after the Celtics blew a fourth-quarter lead and lost to the LA Clippers in overtime. He went 4-for-17 from the field and committed a season-high six turnovers.

And while there were plenty of culprits for Boston's collapse, Walker put the blame squarely on himself.

"I just have to be better," he said.

BOSTON WAS POUNDED by the Philadelphia 76ers in this season's opener, and was losing to the Toronto Raptors entering the fourth quarter of its home opener two nights later. Through his first seven quarters as a Celtic, Walker had shot 8-for-31 from the field and 2-for-11 from 3-point range -- not exactly the kind of production he or the Celtics expected after he signed a four-year max contract in July.

Walker was pressing.

"I just wanted to play well," Walker said. "I wanted to make every shot, and you've got to understand that's not going to happen. I wanted to show the guys that I am a good player. Which I think they already knew."

If they had forgotten, Walker reminded them by scoring 11 points in the fourth quarter against the Raptors, leading the Celtics to the first win in a 10-game win streak that put Boston atop the NBA earlier this month.

Walker is clearly enjoying himself. After eight years in relative obscurity, he's adjusting to playing for one of the league's marquee franchises, and on a roster with plenty of talent. He marvels at the fan support Boston receives on the road ("Even in Charlotte we were getting Celtics chants, which is crazy," he says), and already has fallen in love with playing at TD Garden.

"I had no doubt while I was coaching him this summer that he'd be great for the Celtics given not only his ability on the court but the chemistry he generates with a group," said Warriors coach Steve Kerr, who was an assistant with Team USA this summer, where he coached Walker, Tatum, Brown and Smart. "Everybody loves playing with him. He moves the ball, he plays hard, he's fun to be around."

And while the three-time All-Star is the new face of the franchise -- he is introduced last before each home game, and is the only player who speaks at the podium in the team's news conference room afterward -- he's more than happy to allow others, like Smart and Brown, to take on leadership roles alongside him.

"I don't have to say anything because they're the ones [doing it]," Walker said. "And it's so fun, you know what I mean? I've been the one throughout my career speaking and saying stuff, pregame speeches. Now I don't have to do that stuff because Smart is doing it. If you're not going hard enough in practice, he's speaking up like, 'You've got to pick it up.' Which I love. I love seeing young guys communicating and seeing their leadership skills improve."

Last season, the Celtics revolved around Irving. His play on the court, and words off of it, dictated how things went, and overwhelmed everything else.

This season's more comfortable vibe might have a variety of causes, but it's clear Walker's encouraging approach toward Brown and Tatum is one of them.

For example, when Tatum struggled through a 1-for-18 night against the Dallas Mavericks on Nov. 11, Walker continually picked him up throughout the game, then openly praised him for bouncing back with a 23-point performance two days later against the Washington Wizards.

"I told him that before the game, 'Every night's not going to be the best night. It's all about the bounce-back.' And he bounced back tonight," Walker said. "It was a huge game, it was a big game from home, and that's important -- especially a guy of his age and his caliber, man. He's a special talent, and I'm really excited with the way he handled tonight's game."

All of that filters back to how Walker hopes to guide his teammates through this 82-game campaign.

"There's going to be times this season when things get pretty rough," Walker said. "We're going to hit some adversity, just like every team in this league. So when we hit that period of time, we want to be able to still be together, and not kind of break apart, which can happen."

Last season's Celtics, as talented as they were, did exactly that.

This season's team has new challenges. There are question marks at center. The bench is young and unproven. There is a general lack of size. Overcoming those challenges, though, is easier when a team enjoys playing together. So far, that is true about this season's Celtics.