BOSTON -- By the time Jayson Tatum walked into the Boston Celtics' jersey unveiling event Thursday night, Kyrie Irving had already arrived. Leaning back against the bar (without a drink in his hand, in case you were wondering), he waited for his new teammate to notice him, held out his hand for a greeting, and lit up with the type of excitement reserved for friends.

Moments later, the two talented scorers laughed and laughed at a joke they shared with nobody else. In the overhauled Celtics locker room, Irving and Tatum hold a rare bond: they've actually known each other for years.

"The biggest thing I think that gets kind of drawn over is we're almost complete strangers," Irving said. "We're very big fans of each other's games, but in terms of how we'll collectively mesh as a group, that's a ways away."

A number of other Celtics have preached a similar belief: This could take time. But Irving understands the challenges his new team faces far better than Jaylen Brown or Terry Rozier. With the Cleveland Cavaliers three years ago, Irving experienced firsthand how difficult it can be to throw together a new group of guys -- however talented -- and expect them to win games immediately. Despite adding LeBron James and Kevin Love in a single offseason, that Cavaliers squad fell to the wretched New York Knicks on opening night and staggered to a 19-20 start before ultimately reaching the NBA Finals.

"Man, it takes a long time," Irving said. "And the ups and downs will really define how we are as a group, our identity, and how we respond will be the most important part. That's the only thing that I want to echo here -- you don't want to get too high and too low, I know that's a cliche saying but literally that we want to stay even-keel throughout all of this. Regardless of whatever is happening outside, the only thing that matters is taking care of each other in the locker room."

With only four returners, Irving said the Celtics need to "reshape this whole team and find our identity." They lost four starters from last year's roster, including All-NBA second teamer Isaiah Thomas, as well as two-way threats Jae Crowder and Avery Bradley. Though Irving and Gordon Hayward headlined a list of newcomers that replenished the talent level and then some, this will be a brand new team.

"The best advice is patience," Irving said. "You have to be really strategic and really methodical in not skipping any steps, in order to understand what you want to accomplish and then how to get there. There's a way that you can put a goal at the top but you can't skip any steps that it'll take out you in the mental grind and the physical grind of trying to get back to being at that championship level. We have guys that have some experience, they've seen it first-hand and being part of the culture that I was in Cleveland and bringing that here, that championship culture, that championship understanding."

Added Irving: "We already have an existing culture here with the Boston Celtics that I'm glad to be a part of. But it's been a whirlwind, you know, moving in and picking up my whole life and getting everything adjusted as best I can. So it's been--it's been--man, as you can see I'm at a loss for words because it's been thing after thing after thing after thing."

Irving moved to the Boston area last week and quickly learned one of the most important lessons a Celtics player can take in: it pays to befriend the team's equipment manager, Johnny Joe Connor. After Irving's car broke down near Bentley University, Connor drove to pick up the guard and take him, 45 minutes late, to a meeting with Brad Stevens.

Irving had a good excuse for his tardiness, but the Celtics will need to take advantage of every meeting, practice and game. Hayward knows they have a lot to figure out with an opening-night matchup against the Cavaliers less than a month away.

"I think learning each other's games, learning Coach's system, learning how he wants us to play. What are our strengths? What do we like to do best? You know, just trying to figure each other out, figure out the system, figure out Coach," Hayward said. "Really excited about it. It seems like this summer has been a long summer for me and my family. Excited to be in Boston, excited to finally get started. I know we have a lot of work to do, so we have to get to it."