Isaiah Thomas’ unrequited NBA dream is to reach the playoffs — a goal he may finally realize as a Celtic.

But there’s potential for conflict. There’s another dream — another loyalty — in play. The point guard’s friendship with Floyd Mayweather Jr. has an important upcoming date on May 2 in Las Vegas, when the 38-year-old boxer steps into the ring for perhaps the most important bout of his career against Manny Pacquiao.

Hmmm. The challenge is to make both events work.

“If I can make it, I’m there,” the Celtics point guard said recently. “If there’s something that week, we’re in the playoffs and we have a day off, then I’m going. I’ve gotta be at that fight and show my support.”

Their friendship started five years ago, after Thomas attended a Mayweather workout in Las Vegas. Mayweather, a devoted basketball fan, immediately spotted Thomas in the crowd, arranged a meeting through a mutual friend, and took his new friend to a show.

All in the same day.

“We went to a Robin Thicke concert later that night, and since then, we’ve talked almost every day,” Thomas said of a friendship that has redefined the meaning of gift-giving.

Mayweather, No. 1 on Forbes’ list of the wealthiest athletes with $105 million in reported income in 2014, likes to reward his friends.

Even so, Thomas was admittedly stunned on Feb. 7 when a 2015 Bentley Flying Spur sedan — listed at $200,500 — was delivered to his greater Phoenix home.

“He’s given me a few gifts before, nice ones, but that one was unbelievable. It had everyone in the NBA talking,” Thomas said. “Every team we played after that, guys would come up to me (and ask), ‘Where’s the Bentley, does Floyd got something good for me?’ It surprised everybody.”

The challenge, though, is what to give in return to the world’s wealthiest athlete.

“His birthday just passed. I got him a few nice things, but it’s hard to get someone something who already has everything,” Thomas said. “I can’t get him something like that. But I really thought about the gifts I got him and he liked them.”

Thomas has the car stored back home in Seattle, and would be wise not to expose it to the elements in Boston. But he won’t be able to resist, saying, “I’ll bring it next year. I have to. I’m not going to let it sit around.”

The most important gift, it seems, is the bond that has formed between Thomas and Mayweather, 12 years his senior, who regards him as a young protege, their different sports notwithstanding. Both men are 5-foot-8 and infinitely pugnacious. That was the starting point before they actually met.

“He’s 38, so he’s very old, but he treats me like a little brother,” Thomas said. “It’s weird sometimes. I think, wow, I’m close friends with Floyd Mayweather. Probably the best boxer of all time. But we’ve connected since that day we met.

“He came to games in Sacramento, he was always at our games when we played the Lakers and Clippers. He came to games in Phoenix. Ever since that day I went to see him work out, he’s said, ‘I’ve seen you come to support me, so I’m going to support you.’ ”

Thomas has attended the undefeated Mayweather’s last five fights, including vs. Miguel Cotto, Robert Guerrero, Saul Alvarez and both of the Marcos Maidana bouts. He’s also gone on training runs with Mayweather, generally at the prescribed time of 4 a.m. He’d never dream of asking for a session inside the ring.

“He’s just so serious when he’s in there. When I see him work out he’s in training, he’s in his routine,” Thomas said. “Boxers are on a different level in their training than anybody, I think. When you’re in boxing shape, that’s probably the best shape there is. They do stuff you would never think of.

“You see why he’s 47-0, with his training and regimen. Unbelievable. I’ve never seen somebody work that hard, and be that old at the same level. I try to tell people, if you’re ever in Vegas, go watch him work out. It’s inspiring.”

Mayweather has in turn played basketball against Thomas in games of two-on-two and three-on-three. They’ve never gone at each other one-on-one, though the champ naturally thinks he’s good enough to beat NBA talent.

“He’s just a fan of basketball. That’s all he watches, all day. He thinks he can play,” said Thomas, trying not to smile too derisively. “I mean, he can play. We’ve played basketball before, but he thinks he can play professional.

“He talks a lot of mess, as people know. All he does is talk mess. He’s good, but he’s not as good as he thinks he is.”

Mayweather now has to make a major concession, though. Pacquiao embraced the Celtics during their 2008 NBA title run — becoming their most famous international fan. Could the two rivals actually support the same NBA team?

“Floyd is a fan of whatever team I’m on, so you could say he’s a Celtics fan,” Thomas said, before pausing when asked about the Pacquiao factor. “If he hears that Pacquiao is a Celtics fan, I don’t know what he’ll do.”