BOSTON -- The way Boston Celtics rookie Robert Williams tells it, he routinely showed up to the team's gleaming new Auerbach Center practice facility this summer at 8 or 8:30 a.m., only to see Celtics star big man Al Horford there already -- drenched in sweat, and wrapping up a day's work that began at six.

Horford remembers it a little differently.

"To be honest, I only did that once or twice," Horford said, smiling. "My wife just gave birth, and we have two little ones at home, so I had daddy duty. My kids get up around 8:30 a.m., so I had to get up early, get my work in and get home."

Either way, Williams was impressed.

"I don't know his age, but he's running and jumping with us (younger players)," Williams said. "Every day pace, the constant rate, eating good, working out. Hopefully I can get to that point."

For the record, Horford is 32.

Williams, and any young player looking to attain Horford's level of success to such an advanced age, will find that the key is consistency. Horford began taking advantage of the Auerbach Center almost immediately after it opened in June. Celtics staffers said Horford was one of the first players -- if not the first player -- in the facility after it opened, trying out all the new toys.

Horford's go-to tools include the Norma Tec -- a pulsing post-workout designed to help players heal faster -- and the cold tub. But his favorite addition?

"My new favorite is the float tank," Horford said. "It has nothing to do with recovery, but I come out feeling great. ... It relaxes you, with the Epsom salt and everything. It helps my back. I don't have back issues, but every time I get out of there, I feel taller, because when you're floating, you're not putting on any pressure. You tend to stretch a little bit."

Like most NBA players, Horford is an expert in fitness and recovery -- becoming an elite professional athlete requires a certain amount of know-how. But Horford is part of a tier of players who know the value of durability. His regimen includes fitness certainly, but also diet, recovery and sleep.

That regimen appears to be paying dividends: In the last four years, Horford has played 76, 82, 68 and 72 games (the gap in 2016-17 was due to a concussion), in addition to every playoff game during that span.

"He knows what it takes to be successful, and he's very, very disciplined in his preparation both physically, mentally, skill-wise," Celtics assistant coach Jay Larranaga said. "He gets better every year.

"I don't think we've seen the best version of Al Horford yet, which is awesome considering the career he's had already."

Horford's dedication to self-preservation originated years ago when he was young, watching his father Tito fill hotel-room tubs with ice after professional games overseas -- a far cry from the Norma Tecs and float tanks of 2018.

But Horford began pursuing recovery in earnest in 2013, when a torn pectoral muscle ended his season. That Hawks team made the playoffs, but they did it with a paltry 38-44 record in Horford's absence.

After the injury, Horford began to focus on how he could keep himself healthy. Larranaga said he was one of the first players in Atlanta to hire a personal chef, and that Horford has a staff of people who help him keep his body ready "basically 24 hours a day, 365 days a year."

"(After the injury), it was one of those things that I was like, 'I have to change my game a little bit," Horford said. "I have to be more aware of taking care of my body."

Every player has a pre-game routine. Horford sticks to his religiously --skill work, stretching and (very) politely turning down interview requests if he hasn't completed everything.

"I think it's always being consistent," Celtics forward Semi Ojeleye said when asked what he has learned from Horford. "It's not about going as hard as you can, just not missing days. Some days you're tired, but you come in and get something done so that way your body always stays at a high level."

With a unique stockpile of stars, young prospects and future picks, the Celtics have actively worked to keep their championship window open as long as possible. 29-year-old Isaiah Thomas was a casualty of that window, dealt after two brilliant years in Boston for Kyrie Irving, whose age (25 at the time) lined up better with the likes of Jayson Tatum and Jaylen Brown.

Horford is older than Thomas, and at first glance, his age might make him appear to be an awkward fit as well.

But the Celtics remain excited about Horford's future, even at 32. His skill set lends itself well to the aging process -- more based around fundamentals and basketball IQ than explosive athleticism -- and he's coming off one of the best seasons of his career.

Horford said he feels like his best days are still in the future.

"I actually do," Horford said. "I think I've done great, really well up to this point, but I feel like I keep taking care of myself, working on my game, making improvements, I feel like I have some great years ahead of me."

When the Celtics tore down their roster during the 2013 offseason, their most obvious focus was to get All-Star basketball players. That, after all, is how you win basketball games. But a side-goal was to acquire players who amplified a culture. Al Horford was a perfect example.

Larranaga said he often has Horford address younger players about fitness, recovery and how to prolong their careers.

"He's just a very intelligent person," Larranaga said. "He's very thoughtful. Stuff doesn't happen by chance. His success hasn't happened by chance. It's because it's the result of a lot of hard work, and I think also with all the elite great players, he takes ownership of his career."

What does Horford say in his speeches?

"He always tells us how long the season is," Ojeleye said. "Coming in, you don't really realize how long the season is. It's about being consistent, it's about being efficient. How you sleep, how you eat. Al is always consistent. You never see him come in and not be fresh. He just knows what to do."

Horford's potential for influence is obvious, even to outsiders. He faces daily questions from the media about Williams, a rookie whose defensive potential outstrips even Horford's if his understanding of the team's schemes catches up to his absurd physical tools. Celtics sources said there is a slight reluctance to send Williams to the G-League in Maine, given the good examples that abound on the current Boston roster. That culture directly reflects Horford.

"It's not unique to him, but it's unique to the elite players that there's a consistency to their work," Larranaga said. "There's not a lot of emotion in his decisions. It's, 'This is what's right, and I'm going to do it every day. Maybe I'm not gong to see results in the first day or the second day, but I trust that over time it's going to pay off.' He's just so consistent with his work ethic, his preparation, his emotions. He's special."

Consistency isn't something young players understand immediately, but it can be learned. Ojeleye works on his shooting before and after every practice, and before every game. Williams has been a model citizen since his early slip-ups. If Horford impacted them, that's yet another benefit he brings to the table for the Celtics.

"It took me a lot of years to understand everything that it took to be at a high level," Horford said. "Not only on the court and in the weight room, but also making sure that I'm taking care of my body, that I'm recovering. It's a year-round process. It's not just in-season and then offseason and it's over. As you grow and you learn, you start figuring those things out."