BOSTON -- The moment Billy Donovan learned what kind of competitor Al Horford is remains as clear in his memory as if it happened this week -- and not 20 years ago.
Donovan was deep into a recruiting battle to sign Horford -- then a leading prospect out of Michigan -- and went to watch him play in the Adidas Big Time Tournament in Las Vegas.
Horford's Michigan Mustangs had made, in his words, an "improbable" run to the title game, where they faced the Atlanta Celtics -- one of the greatest AAU teams ever assembled -- who boasted future NBA stars Dwight Howard and Josh Smith. The Mustangs lost by 20 points.
"It was one of those games where it was hard-fought," Horford says now, "but they were the better team."
Donovan, though, remembers the tilt for another reason.
"I'm in the gym, and I'm walking off the court out of the stands to leave," Donovan says, "and [Horford] was over on the side of the bleachers -- by himself -- crying.
"And I'm like, 'You know what? Here's a guy, at 17 years old, who cares about winning.' I can't express that enough with the guy. That's all it's about."
As Horford walked out of TD Garden on Wednesday night after helping the Boston Celtics claim Game 3 and a 2-1 series lead over the Golden State Warriors heading into Game 4 of the NBA Finals (9 p.m. ET Friday, ABC), he smiles as he thinks back on that day.
"I remember it very vividly," Horford says. "For me, I'm a big competitor. People channel that in different ways. But I hate losing, and it's something that really drives me.
"[Donovan] shared that moment with me years ago ... We're kind of built like that. We hate losing and do everything we can to win."
The two of them would go on to win plenty of games together. Not only did Donovan win that recruiting battle, he and Horford's Gators were the last team to repeat as national champions, in 2006 and 2007.
Fast-forward through a 15-year NBA career and Horford now finds himself two wins from his first championship in his breakthrough Finals appearance.
But this time last season, Horford was sitting at home, watching the playoffs on television and wondering whether any of this was possible.
"I would look on my phone at photos [to see] exactly what I was doing at the moment," Horford said following Boston's Game 7 victory over the Miami Heat in the Eastern Conference finals. "I always look back and see where I was just day to day."
Horford's NBA future before reuniting with the Celtics couldn't have been murkier. Two seasons ago, he fell out of the starting lineup with the Philadelphia 76ers. A trade to the Oklahoma City Thunder and a lost season with OKC followed -- his first time missing the playoffs in 14 seasons -- and two years remaining on his contract left his situation in flux.
Horford didn't know if he'd still be with the Thunder or if he'd be anywhere with a chance to win, but he has taken full advantage of the life preserver thrown to him by the Celtics, the team he left in free agency three years ago.
"It's just special to be with them and be able to help them and be a part of this," Horford said after that Game 7. "I'm really grateful to be in this position."
'Continuing to reinvent myself': An awkward fit in Philly
When Horford signed with the Celtics in 2016, it was a seminal moment for the franchise.
After a free-agency battle that had come down to the Celtics and Washington Wizards, Horford's decision to join Boston -- a city that hadn't won recruiting battles in the past -- helped set the stage for Gordon Hayward to join a year later and Kyrie Irving to arrive via trade a couple of months after that.
Horford's versatility at both ends helped lead Boston to the East finals in 2016-17 and 2017-18. But in the summer of 2019, Horford chose to opt out of his contract, stunning the NBA world by leaving the Celtics for the division-rival 76ers -- who already had star center Joel Embiid on the roster.
"I've always been a fan of Joel and just everything he brings on the court, off the court. There were some great battles," Horford said during his introductory news conference. "When this opportunity came along and the possibility of teaming up with him, [it] got me really excited about the potential."
A few months later, amid a clunky on-court fit next to Embiid, Horford flipped his tone.
"It's almost like me continuing to reinvent myself," Horford said midway through that season, "and trying to figure out other ways that I can be effective."
Horford performed well in his stints at center with Embiid off the court, proving to be a good fit with point guard Ben Simmons in those minutes. But it was a sparing role, and Horford struggled to adjust to his new reality as a floor spacer; he shot just 31.8% from 3-point range that season.
Celtics coach Ime Udoka, who was an assistant in Philadelphia that season, said Horford's role in Boston is far different than with the 76ers, admitting it was an awkward fit from the start.
"We've emphasized him taking advantage of his size when teams [guard him with smaller players]," Udoka says. "[And] when he asked what I was looking for from him, it was to be able to switch on the perimeter, which is different than how we guarded in Philly.
"And then make 3s, shoot for 40%-plus [and] have more of a green light than he did in Philadelphia."
The 76ers were matched up with Horford's old team in the first round of the NBA playoffs inside the league's 2020 bubble in Orlando, Florida, and he spent the series scoring a combined 28 points across four games, failing to hit a single 3-pointer while getting spun around in circles on defense.
"He was tasked with guarding Jaylen Brown in that series," Celtics president of basketball operations Brad Stevens says. "That's not an easy spot to be in for anybody."
Daryl Morey -- in his first move as president of basketball operations in Philadelphia -- sent Horford, along with a first-round pick, to the Thunder in a draft-night deal in exchange for guard Danny Green.
"I think the theme tonight," Morey said that evening, "was trying to improve the fit."
It also was about shedding the final three years and more than $60 million guaranteed left on Horford's deal at the time.
In Oklahoma City, Horford's future became even more unclear.
'Where I wanted to be': A lifeline after a lost season
Horford's arrival to the Thunder was part of a full franchise reset.
Chris Paul had just departed in a deal with the Phoenix Suns, as Thunder executive vice president Sam Presti accumulated one first-round pick after another to add to a young core led by guard Shai Gilgeous-Alexander.
While Horford showed he could still be an effective starting center across 28 games with the franchise, averaging 14.2 points, 6.7 rebounds and 3.4 assists while shooting over 36% from 3-point range, the two sides agreed to shut down his season in March.
"We've talked with Al from the time he became a member of the Thunder this offseason about the many ways in which he would be able to help us as we entered the early stages of the necessary transition of our team," Presti said in a statement at the time the decision was made.
"Our conversations have been open and ongoing about how to maximize this season for him personally as well as the development of our team. Al has been nothing short of spectacular and will remain a part of the team as we build on an approach and mentality that we have taken for some time."
Translation: There was a need to move Horford aside to allow younger players a chance at minutes and to ensure the team had the best chance possible of getting some lottery luck.
But while Oklahoma City's direction was obvious, Horford's career path was not.
He was a 34-year-old center in a league where fewer and fewer of them are getting paid significant money, and he had at least $40 million guaranteed over the remaining two years of his contract. At the time, it seemed very possible he could be stuck in basketball purgatory for another calendar year.
Things in Boston were just as ugly. The Celtics fell flat last season, going 36-36 and getting routed in the first round of the playoffs by the Brooklyn Nets.
Kemba Walker, the team's maximum salary point-guard replacement for Irving, who'd unceremoniously departed for Brooklyn in the offseason, had gone from tormenting Philadelphia in the bubble to being unable to finish the Nets series due to ongoing knee issues.
When the series ended, longtime president of basketball operations Danny Ainge stepped away from the team, and Brad Stevens, after eight years as coach, moved upstairs to replace him.
And, two weeks into his tenure -- just as Morey had during the prior offseason -- Stevens made his first move: a trade involving Horford. Walker was dealt to Oklahoma City, along with a first-round pick, in exchange for reuniting Stevens with one of his favorite players.
"The financial flexibility was certainly a part of it," Stevens says. "But Al had played really well in Oklahoma City. The fit in Philly was the issue, not his play, or his mobility or anything else."
For Horford, the trade represented something else: a lifeline.
"When I got the call from Brad, it was really, really exciting," Horford said during NBA Finals media day. "I remember I was driving home with my family from visiting my mom in Atlanta, and we got the call. We were just all screaming in the car. ...
"It was a really happy time for my family at that time. Especially for me, because it's where I wanted to be."
'When he came back, that gave us a sense of security': What Horford means to Boston's run
As the Celtics basked in the glow of reaching the NBA Finals for the first time in 12 years, one specific sentiment filled most every conversation: a universal thrill for Horford.
"Nobody deserves it more than this guy on my right, right here," Brown said while sitting next to Horford on the podium after the Game 7 win in Miami.
"His energy, his demeanor, coming in every day, being a professional, taking care of his body, being a leader, I'm proud to be able to share this moment with a veteran, a mentor, a brother, a guy like Al Horford."
"Al could care less about the numbers," Celtics guard Marcus Smart said. "He cares about the wins and this team. When he came back, that gave us a sense of security."
Horford has been far more demonstrative than usual during these playoffs, repeatedly showing emotion after making big plays.
"That's fair," Horford said with a smile ahead of Game 2 of the Finals. "I just think that it's the playoffs ... a lot of emotions, and I feel like as we keep going along, it just keeps getting more intense."
While he never found the right fit next to Embiid, he has developed brilliant chemistry with Robert Williams III as the dual fulcrums of Boston's league-leading defense, as Boston's 99.9 defensive rating with the two of them on the court was the best of any pairing of Celtics players who played at least 400 minutes together this season, according to ESPN Stats & Information research.
Horford's passing skills helped unlock Boston's offense as the season progressed, as the Celtics posted an NBA-best offensive rating of 120.2 over the final 35 games of the regular season.
It was something Udoka saw coming as early as the first time he saw Horford following this summer, and how energized he was to be back in Boston.
"Once I saw him in training camp, he was great from day one," Udoka says. "His body looked like it had changed, and I think a big part of that was being motivated to come back here, where he had success.
"He's carried that throughout the whole season with all the ups and downs. He's been one of our most consistent [guys] ... and from there, he's stepped it up even more so in the playoffs."
While Horford's steadying presence throughout has played a huge role in Boston's run to the Finals, two performances stood out: a 30-point outburst in Boston's Game 4 win in Milwaukee, dragging Boston back into that series and restoring home-court advantage, and 26 points and a career-high six 3-pointers in Game 1 in his Finals debut.
"Al is like the best teammate ever," Tatum said before Game 1. "The same guy today that he was in my rookie year, welcoming everybody, doing what's best for the team and sacrificing touches for himself.
"Just to see how happy he was to get to this point ... I felt like I had been playing forever, finally getting over that hump, and it's like, I've only been doing this for five years. It's his 15th year."
For Donovan, hearing players talk about Horford's value in the locker room, and how much he means to them, comes as no surprise.
"You never ever, ever, ever," Donovan says, "question where his heart's at.
"Sometimes [for] younger players, as they're trying to establish themselves in the league, it becomes first like, 'OK, I've got to establish myself, I've got to earn a contract. And once I do those things and take care of me, then I'll focus on winning.' He's the opposite ... It's always all about winning."
After a circuitous three years, a stretch in which his fit and future were questioned, Horford is back in Boston -- chasing a title for the first time.
"The way that I took it was 'I'm just going to put my head down,'" Horford said before Game 2 of the Finals, "and continue to work during those years in Philly, during the year in Oklahoma, get better, and wait for my time.
"I knew the time was going to come."