BOSTON – A few days before his annual YounGameChanger Foundation Bowling Bash, Marcus Smart received a surprise text from former teammate Isaiah Thomas. It just so happened that Thomas and his new team, the Washington Wizards, would be arriving in Boston Tuesday afternoon, just a few hours before the event was set to begin. He wanted Smart to know that he wouldn’t be missing it for the world.

“He just said he wanted to come and support and my eyes lit up,” Smart told to Celtics.com at Wednesday morning’s shootaround before facing off against Washington. “That meant a lot to me. For Isaiah, he didn’t have to do that. He could have done anything else on his night off before a game, but instead, he decided to come out and support me.”

Although they were teammates for only two and a half years, Smart and Thomas forged an incredible bond – a bond that continues to carry on despite them now being on opposing teams.

“Me and Isaiah built a relationship that will go beyond basketball for years,” Smart said. “It’s more of a friendship, more like a brotherhood for me and him.”

They connected right from the beginning in Boston. The pair shared a lot in common, most notably the tenacity with which they both displayed on the court night-in and night-out.

Because of that tenacity, both players became beloved by the Celtics fanbase. The appreciation for Thomas, in particular, was off the charts during his time in Boston, as he displayed unbelievable persistence, playing through multiple injuries and even through the tragic death of his younger sister during the Celtics’ 2017 Eastern Conference Finals run.

“What he did for this team in his time here, going through what he went through with his sister, his family and everything that he was going through, he still came out and poured his heart out every night and every day,” Smart said. “When you’re in Boston, we all know how Boston fans love that. So, he means a lot to this city. He is this city. And he put his heart and soul into this court every single night.”

Smart watched as Thomas’ hard work paid off in the form of an All-NBA selection in 2017, after a season during which he averaged an Eastern Conference-leading 28.9 points per game, while making a team-record 245 3-pointers.

Since that campaign, however, Thomas’ career has been on a roller coaster. At the end of the 2017 offseason, he was traded to Cleveland and wound up sitting out for about half of the regular season with a hip injury before being traded to the Los Angeles Lakers. The following season, he went to Denver, where his role for the Nuggets was limited.

This past offseason, Thomas signed with the Wizards, but more health problems ensued as he had to miss all of training camp and the preseason, along with the first few games of the regular season with a hand injury.

Seeing Thomas go through all of that was heartbreaking for Smart.

“I don’t wish injury upon anybody, not my worst enemy, and especially not a guy who has worked so hard to get where he’s been,” Smart said. “To get to where he’s been, coming from the last pick in the draft to being an All-Star, to setting numbers and records like he did. It’s hard for us, and for me personally. Because like I said, I’ve been here with him. I know what he’s capable of; I’ve seen it. But he’s a fighter. He’s resilient.”

That resiliency has shone through over the last few weeks, as Thomas has returned to action and seems to be on track for a solid comeback campaign. During his six appearances, Thomas has put up 13.2 points and 6.2 assists per game, while averaging of 22.7 minutes of playing time.

“I think it's about time,” said Jaylen Brown, who is the only other remaining Celtic who played with Thomas in Boston. “We know Isaiah's talent. His health has been up and down, but it's good to see him healthy and that somebody gave him a chance, and he's doing well with it.

“You can't keep people like that down for long,” Brown continued. “It's only a matter of time for him to have a breakout game, or breakout season or something. But it's good to see him back out on the court where he belongs.”

Seeing Thomas show signs of returning to form makes Smart’s eyes light up just as much as they did when he received that surprise text a few days ago.

“When I see glimpses of that '16-'17 IT, I get excited every time,” he said with a smile.

Heading into Wednesday night, Smart is excited for a different reason: having the opportunity to put the clamps on Thomas as the former All-Star point guard returns to TD Garden. The pair will be enemies for 48 minutes on the parquet floor, but once the final buzzer sounds, their everlasting friendship will pick up right where it left off.