BOSTON – From his spacious office inside the Auerbach Center, the Celtics’ glistening 70,000-square-foot practice facility that officially opened in June, Brad Stevens is getting antsy. It’s been a little over two months since Boston’s season ended, since LeBron James sent Stevens’ team packing for the second straight season. Training camp officially opens in late September — which, for Stevens, can’t come soon enough.

“We were all disappointed with how it ended,” the Celtics coach told the Yahoo Sports NBA podcast. “That was the beauty of that team — it didn’t really buy into everybody else’s thoughts … We’ll all improve from the experience, but there’s no question, we’re itching to get started.”

And why wouldn’t he? Since the NBA Finals ended and James took his talents to Manhattan Beach, everyone is talking about Boston. Favorites to win the East. Co-favorites to win the whole thing. The Warriors seemed to cinch up a third straight title with the signing of DeMarcus Cousins, but this Boston team — 3-3 against Golden State the last three years, with Stevens’ effective, switch-happy defense a key reason — is being given at least a puncher’s chance at a title. Oddsmaker SuperBook projects the Celtics to win 57 games; BetDSI has Boston at plus-575 to win a championship — second-lowest odds of any NBA team.

All of this means real expectations — a first for Stevens in Boston. The Celtics have been a rebuilding team under Stevens (a 25-win 2013-14 season, his first in Boston), a surprise contending team (the 53-win ’16-17 season) and an overachieving team (last year’s injury-plagued 55-win campaign). When next season opens, expectations will be, at a minimum, a conference championship.

How does Stevens approach a season like that?

“The beautiful part of keeping a day-to-day mindset of trying to improve every day is that no matter what your expectations are — whether you are at the beginning or the building stage or you have a team like we do, that’s bringing a lot of guys back, that is trying to reach a next step, or you’re Golden State and you have won three of the last four championships — if you’re focused on the day and getting better that day, everything takes care of itself,” Stevens said. “Our challenge is to be the best version of ourselves.”

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Still, the expectations will be lofty. There will be expectations on Kyrie Irving, the All-NBA point guard who thrived in his first season in Boston before a balky knee robbed him of the last third of it. Last month, Irving revealed details of the severity of his knee issues — bacteria that had built up nearly caused a staph infection, Irving said — but declared that he would be ready for training camp. Irving’s free agency next summer will be a frequent talking point — though not between Irving and Stevens.

“I’m not going to talk to him about it at all,” Stevens said. “One of the things I want to do is give everything I can to all these guys while they’re here. Hopefully, the people that are here recognize that it’s a really good environment with a high upside for a long time. It’s some place that will be committed to them, committed to their overall game and enhancement and off the court and everything else. There’s no real discussion to be had. It’s more, ‘We can’t wait to get to work.’ ”

There will be expectations on Jayson Tatum, the rookie phenom who stepped into the starting lineup as a 19-year-old and shattered any and all expectations. Stevens can’t pinpoint the moment he realized Tatum was really good (“There were a lot of them,” Stevens said), but like everyone else, he’s giddy about Tatum’s future. Tatum has placed a priority on strengthening his sinewy 6-foot-8, 205-pound frame, and Stevens says Tatum has been around the facility during the summer working toward that end.

“Being able to play lower, longer requires a significant deal of core strength for any player, certainly for a younger player with size,” Stevens said. “That’s really been our emphasis, to continue to focus on the core strength of things.”

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