Where would Isaiah Thomas and the Celtics be without each other?

On the Suns' bus, word arrived that Dragic had been dealt to the Miami Heat. Thomas recalls a sense of relief washing over the bus, as players were excited that the backcourt logjam might ease.

The deadline passed, but news about deals was still trickling out. Wright, who had been traded from Boston to Phoenix one month earlier, stood up and announced, "IT, you just got traded!" Thomas thought it was a joke. A Phoenix assistant coach climbed onto the bus a couple minutes later and confirmed the news.

All the Suns got in return for Thomas was veteran guard Marcus Thornton and a 2016 first-round pick (it was Cleveland's pick and checked in at No. 28 that year). Suns general manager Ryan McDonough, who cut his teeth in Boston's front office, later admitted, "If I could get a mulligan, that'd be it."

Gerald Green, who often shared the floor with Thomas in Phoenix during that 2014-15 season, said the two talked often about how they might thrive in the right situation. Green signed with Boston this summer, in large part because of Thomas' presence and the Celtics' status as contenders in the East. It doesn't surprise Green to see Thomas flourishing.

"We didn't want to see Isaiah go [in Phoenix]," Green said. "We were kind of blown away when he got traded because he was really one of the guys that kept the team pumping, on and off the court. So when he got traded, we kind of felt down as a team in Phoenix. We knew he was going to be successful here in Boston. We didn't know just how successful he could be.

"Just to see him to that point and this point now, I just smile, man. He was a guy that one team didn't want him, two teams didn't want him, and now a team like the Boston Celtics, who have championship aspirations, are just in love with him. It just makes me smile, man. It's kind of like looking at your little brother grow up."

'Isaiah was what we needed'

Stevens isn't one for hypotheticals, but presented with the question of where Boston would be without Thomas, he admits that Thomas' arrival was exactly what this team needed to move forward at that point.

"I've never really thought about [what might have happened without Thomas], but it made us different because we had a guy that -- and I've said this many times -- Isaiah was what we needed," Stevens said. "There's no question about that. And the players around him make him better too. I think he is such a good fit for the guys that are here, and they are such a good fit for him. And that's why it works, right? He's been great. It's fun having him around."

It's easy to forget now, but the Celtics' roster was in a constant state of flux during that 2014-15 campaign, in which Boston carried a staggering 40 different players. The roster overhaul really started in December, when the team traded Rajon Rondo, the last holdover from the 2008 title squad, to Dallas in exchange for a package that included Brandan Wright, Jameer Nelson, Jae Crowder and draft picks.

Crowder, used to playoff appearances in Dallas, remembers being leery of what Boston was trying to do, so much so that he confronted Stevens after a practice in January and demanded to know if the young coach was OK with tanking. Stevens was adamant that his lone focus was getting better, and the Celtics, a .500 team through mid-January, started making the sort of progress that calmed Crowder in the month leading up to February's trade deadline.

That progress also gave Celtics president of basketball operations Danny Ainge confidence to explore moves that had the potential to make the team better at a time when some wondered if Boston's rebuild would be better served by stripping talent and losing games.

"I think the biggest thing for us was, under most circumstances, [the Suns deal] would be a trade that we would do because of how we felt about Isaiah, all day long," Ainge said. "The only downside was we were going to get better in the second half of the year, when there wasn't much hope for us to really contend."

"That was the biggest question that, ultimately, it came down to. We just liked Isaiah better than a few spots higher in the draft, and we ended up making the playoffs that year, and I think that was good for lots of reasons -- just the morale of the team and our coaches.

"More than anything, we ended up getting a player that's hard to find in any draft, let alone going from -- what did we pick, 16 that year? If we had not done the deal, we probably would have ended up at maybe 12 or 13, I don't know. And we got Terry Rozier with that pick, who's going to help us this year."

'It's crazy to see Tom Brady's name on my phone'

Despite everything he has accomplished the past 20 months, Thomas is far from satisfied. He is enthralled by the success of others at the pinnacle of their sport. That's why he's close with boxer Floyd Mayweather Jr. That's why, in a summer filled with adventures, he ranks getting to meet Hall of Famer -- and childhood idol -- Allen Iverson as maybe his biggest thrill. Also, after they exchanged numbers at the Durant pitch in the Hamptons, Thomas now casually exchanges text messages with New England Patriots quarterback Tom Brady.

"It's crazy to see Tom Brady's name on my phone. It doesn't seem real. Just like playing for the Celtics and being that guy doesn't seem real," Thomas said. "Like meeting David Ortiz and him knowing who I am, all that stuff doesn't seem real. I'm blessed, man. And I don't take it for granted because a year and a half ago, it was like, I was the third-string point guard. Years before that, I was the 60th pick. A lot has changed, and it's been nice."

What hasn't changed is Thomas' desire to improve. Thomas averaged 22.2 points and 6.2 assists per game last season, and that barely tells the story of how important he was to Boston's offense. He's eager to prove to naysayers that he can maintain an All-Star level of play and continue to evolve his game. But what matters most to him is proving he's a winner, and his No. 1 goal is to take this team deeper in the playoffs.

"I just know the great players never get satisfied," he said. "I'm trying to put my name in the same categories as those players, whether it be Floyd Mayweather, Tom Brady. I'm trying to learn from them and use my platform to be able to reach out and have relationships with those great players because I want to see how they think.

"I don't know it all. I don't know how to win at a high level when it comes to winning playoff series. But I want to learn. I think that's the best thing about the great players: They want to learn, they are willing to learn, and they are willing to get better."

The Celtics starters endured some bumps early in training camp while integrating Horford -- mostly because everyone was being too unselfish -- but preseason play suggests the first unit should be one of Boston's strengths. Horford is such an ideal fit for this team, particularly the way he moves the ball offensively, and his back-line defense will help a team that tied for the fourth-best defensive rating in the league last season.

Even better, Horford's quiet demeanor allows Thomas to remain in the spotlight. Before preseason games at TD Garden, Thomas was announced last, with Horford coming out a spot before him during starting the lineup.

"Al's an easy guy to coexist with," Stevens said. "There's no question about that."

Thomas recognized that more talent was needed to get this team where it wanted to go. He would have been fine sacrificing some of his own spotlight if the team could have hooked Durant, and Thomas wants Ainge to keep swinging for the fences. Thomas knows that more talent helps make the game easier for him. He's thrilled to have Horford as his new running mate; it even allows Thomas to shoot for loftier goals, individually.

"I want more. I tell people: I want to be All-Star, I want to be All-NBA, one day I want to be an MVP," he said. "That's not just me talking. That's goals that I have. Being on the Boston Celtics and being able to win and make the playoffs, those are achievable."

Thomas, motivated highly by those who think his All-Star appearance last season was a fluke, has looked very much like a player hoping to get a return trip this February. Through Boston's first three games, Thomas is averaging a team-best 24.7 points per game while shooting 53.1 percent from the floor. Boston's offensive rating is 107.9 points per 100 possessions when Thomas is on the floor.

Thomas can become the third Celtics player in the past 50 years to average 24 or more points in Boston's first four games on Wednesday against the Bulls, and would join elite company in Paul Pierce and Larry Bird.

It's fair to wonder where Boston would be if that 2015 deadline had passed without activity. How would morale have been after another trip to the lottery? How would the Celtics have added talent without establishing a winning environment?

Where would the Celtics be without Thomas? It seems fair to say the future wouldn't look quite so bright.