Marcus Smart, center, said he was blindsided when the Celtics traded him to Memphis as par tof the deal to acquire Kristaps Porzingis, left. Steven Senne/Associated Press

Marcus Smart went to sleep on June 21 still a member of the Celtics and fully expected it to be that way when he woke up.

But when he did wake up, the longtime Celtic was blindsided by the news.

On Sunday, Smart spoke publicly for the first time since the Celtics traded him to the Grizzlies, as he talked to reporters at the Dana Barros Basketball Club in Stoughton, Massachusetts, where he was given a Boston send-off at his 14 League Pro-Am Tournament. The point guard said he learned about the trade involving Kristaps Porzingis after his agent called his fiancee, who woke him up to tell him the stunning news.

Smart didn’t expect it, mostly because he was just told it wouldn’t happen.

“It was definitely shocking to find out that way, especially because the week before I was already told that we were good and there was no trade talks of me and I was good, so we were expecting that,” Smart told reporters. “But for me, I understand the business side of it. I’ve always been like that and anybody who knows me knows that I’m the first one to tell people you can’t put personal with business, it just doesn’t mix and if you do, you’re going to get yourself hurt. So, I understand that it’s a business.”

Still, Smart expressed disappointment that he found out the way he did.

“It was just the courtesy,” Smart told reporters. “They probably already knew that they were thinking about trading, they had this trade in their back pocket just in case something else didn’t happen. And for me, it’s just a simple fact, ‘Hey, we’re thinking about trading you, most likely we’ll trade you, just letting you know.’ Thank you, I appreciate that, especially with everything they’re telling me the week before and then my house flooding and having to deal with that, so it was a lot all at once.”

It was also a lot for Celtics’ fans to process.

Almost immediately after the trade broke, social media was flooded with shock and disappointment from fans who adored Smart, who became one of their own over nine seasons. He’s seen the messages, and he’s heard from plenty of people, too. Smart has stayed in the area – he continued his annual two-day basketball clinic in Westford last week – and has truly felt the support.

“I grew up here,” Smart told reporters. “Nine years here in the city, … I’ve built a special bond with the fans and the people of Boston. I don’t think there’s a place in Boston that I can’t go where I wouldn’t be welcomed. That speaks volumes. It’s definitely tough. I’m hearing it all the time from everybody, the fans, every time I see them. They’re devastated. The city is devastated. And I understand why. We grew up together, so it’s definitely tough, it’s definitely hard to say goodbye.

“I know talking to some of these fans, I definitely get emotional. They’re coming up to me and they’re bawling, so I definitely have heard everybody’s disappointed. But like I said, it’s a business first. Boston will always be in my heart. I love Boston. But they decided … they made a move they thought was best for the team, and that’s all you can ask for.”

Smart said all of his Celtics teammates have reached out to him since the trade, and he made a point, unprompted, to shut down rumors that he and Jaylen Brown have issues with each other. Brown didn’t post about Smart on social media like Jayson Tatum did, which sparked internet speculation that Smart felt the need to address.

“I actually want to clear up something. I’ve seen online that was going around that because J.B. didn’t post something about me like J.T. did, that we had beef,” Smart told reporters. “Jayson and Jaylen are my brothers for life, and I don’t think what people see isn’t enough of what and how our relationship really is. We’ve been through a lot together, we’ve been through the fire. My mom passed away, JB was actually one of the people on that plane that came to Dallas to the funeral. So I just wanted to shut all rumors down now that me and J.B. had beef.

“I have no beef with anybody with the Celtics. None of my teammates. I love those guys, they love me. We’re brothers, and I know that if I’m ever in need or need or want anything, I can call those guys and vice versa. But me and J.B., we’re great. That’s my brother. He actually texted me and he was just as disappointed as I was, so we’re good. Just because J.B. or any of my teammates didn’t post anything doesn’t mean that we have beef or something’s going on.”

As hard as it’s been for him to say goodbye, Smart is excited for his next chapter in Memphis, where he noted that he’ll be the second-oldest player on the Grizzlies behind Steven Adams. He’s excited to serve as a mentor for Ja Morant and a leader on a young, contending team. He’s moving on while still processing emotions about what the last nine years have meant to him.

“I’ve loved the journey that I’ve been a part of with this organization, with this team,” Smart told reporters. “I couldn’t ask for more. … I’ve enjoyed my run. Very thankful to the organization, to the city, to my teammates for allowing me to be me, and really taking me in, a Dallas kid from the south side, Lancaster, Texas, transferred to Flower Mound and then came up here to Oklahoma State and then came to Boston, so to be able to take me with everything I have, who I am and just allowing me to be me, I say thank you. …

“I love this team. I love this organization. I love the people, the fans, the support I have always gotten from my nine years. I’m definitely going to miss it, but I’m excited and energetic to start my new chapter in my life with the Grizzlies.”