Sprints to start certain practices.

Star players coasting through others.

Live goal-line periods cracking with colliding helmets and shoulder pads for the first time in two summers.

Through 10 practices, Patriots training camp has been an exercise in the familiar — welcome back, Bill O’Brien — and in firsts. Most changes, particularly O’Brien’s return, have been welcome and productive, as the team’s offense springs to life again. But certain scenes have stupefied, even rankled, some ex-players; namely, how Bill Belichick could be content with his best players sitting out a combined dozen practices before the team’s first preseason game.

“It’s so weird that Bill would let that happen,” said ex-Pats linebacker Rob Ninkovich of Matthew Judon’s contract “hold-in.”

Under Belichick, the rule used to be if you can practice, you practice. No excuses.

Now, it depends.

“Honestly, you’ve got to ask Bill Belichick,” star running back Rhamondre Stevenson said this week. “I don’t know why I’m not practicing.”

Judon’s extended absence likely resolved late Friday night, when he agreed to terms on a desired reworked to guarantee $12 million more than it originally contained. Reportedly, the Patriots and Judon also agreed to keep him on a practice pitch count, something the four-time Pro Bowler mentioned during his only press conference this summer.

Removed from the team’s longstanding history of long and laborious practices, resting Judon is sensible. Normal, even, for other teams. Judon is both an established star coming off a career year and a veteran who can fairly be criticized for fading toward the end of each of the past two seasons. Though Judon is not alone in that failure.

The Patriots have not finished a season strong since 2017. They fell apart down the stretch of their two most recent playoff campaigns and last year. Perhaps those failures are motivating Belichick’s apparent flexibility on practice participation – elsewhere labeled as “load management” – a theory that’s been floated inside and around the facility.

But whatever is driving these changes may not be as interesting as who.

Last week, Belichick cited three people when asked about the influence his athletic support staff has on changes he enacts at his training camp schedule: head strength and conditioning coach Moses Cabrera, head athletic trainer Jim Whalen and director of performance and rehabilitation Johann Bilsborough.

“Their respective staffs give input, talk to the staff, talk to the coaches about what we need to do, where they feel like we’re at, etc.,” Belichick said. “And we make the best decisions we can to be as productive as we can on the field.”

Whalen and Cabrera are close to Patriot lifers, men who have spent roughly 35 years combined with the organization over their careers. Along with assistant strength and conditioning coach Deron Mayo, Cabrera builds players up daily through individualized workout regimens, while Whalen builds them back by overseeing the evaluation of any injury, its treatment and rehabilitation.

Bilsborough, however, is less understood – even by fellow members of the organization.

“That department is like a black box for most people,” a team source told the Herald.

According to the Patriots’ media guide, Bilsborough began working for the team in 2016, shortly after he completed his first of five years with the Boston Celtics. Belichick recruited Bilsborough after seeing his work under former Celtics head coach, current president of Basketball Operations and friend, Brad Stevens. The C’s originally hired Bilsborough from his native Australia, where he came up working for the Australian Football League, rugby teams and mixed-martial artists.

His sports science duties for the Celtics involved quantifying players’ sleep, recovery and the energy they expended on the court and in the weight room; all in the name of maximizing performance.

“It’s trying to find the cluster of really important factors that we believe are the most important,” Bilsborough explained in a 2015 Herald article. “In the previous sports I’ve worked in, we’ve looked at the movement patterns on the field, some of the heart-rate measures we would take to see what zones they’re in relating to the stimulus of the practice session, and then we’d look at some subjective things as well — how they’re feeling.”

Among other day-to-day responsibilities in Foxboro, Bilsborough and his staff track how far and fast Patriots players run in practice. They measure the force players apply with certain movements, and hold this data against each player’s previously established baselines of physical capability. Any drop-off could indicate fatigue or perhaps growing risk of injury.

The data helps inform decisions made by Cabrera’s crew, the coaching staff and the man making every call on who sits and starts for the Patriots, be it a practice or game: Belichick. But according to another source, while Belichick seemed to like the data in Bilsborough’s early years – maybe he didn’t love it.

The structure and intensity of practices largely went unchanged from the time Bilsborough arrived to as recently as the last few seasons. For example, according to sources, Belichick pushed players through a physical padded practice in late December 2019 before the Patriots’ regular-season finale against the 4-11 Dolphins. Days later, the Pats lost to Miami as 16-point favorites and cost themselves a first-round playoff bye in Tom Brady’s final season.

“I don’t think they used (the data) that much, to be quite honest,” a source said. “Guys would run a lot of yards, and it would show maybe they should slow down. And then they’d have to do the same thing the next day.”

Whether or not the Patriots have since embraced the teachings of sports science (Bilsborough and his staff left the Celtics shortly after that Miami loss to work full-time in Foxboro), Bilsborough’s presence has remained steady inside the facility. Like Cabrera, his office resides inside the team’s weight room. Bilsborough and Cabrera are in constant contact with one another, players and Belichick, according to one source.

On Friday, a few Patriots assistant coaches opened up about the impact of his work on their day-to-day operation.

“(Bilsborough and Cabrera) do a great job of giving us information that they get that, up until the last few years, I had no idea what it even was,” said linebackers coach Steve Belichick. “The tracking systems, the speeds, the yardages and stuff like that … I learn a lot from them, and (about) trying to prevent things from happening based on who the player is, and the numbers and information that we get from those guys.”

Inside the building, Bilsborough is regarded as affable, someone who can cross into coaches offices as easily as the locker room. He’s known to connect and joke with players.

“The best sports science is having dialogue with the player,” Bilsborough said in 2015. “You can’t run your program with just numbers.”

And yet, the core of Bilsborough’s work remains data-driven.

“You have to be a nerd for that job,” one source said. “He definitely is.”

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Bilsborough is one of dozens, perhaps hundreds, of sports scientists working today across the NFL. Nowadays, it's perfectly common for players to receive rest days at practice, down nutrient-rich smoothies after leaving the field and wear GPS tracking devices. UCLA coach Chip Kelly, a Belichick confidant, is credited with popularizing football's embrace of the field when he was the Eagles' head coach from 2013-15.

A year after Kelly was fired, Bilsborough first set foot in Foxboro. Seven years later, his work is finally being recognized.

"I don't know much about the stuff that they do, but they're really good at," Steve Belichick said. "If you could get through the Australian accent, if you can gotta navigate that, I think we've worked really well together."

Former All-Pro cornerback Darrelle Revis spent most of his career torturing the Patriots.

His 2014 season was a notable exception.

Revis was a member of the Patriots' Super Bowl-winning team that season, an All-Pro who signed a short-term deal with his former rival to chase a ring. On Saturday, Revis was inducted into the Pro Football Hall of Fame as a member of the Hall's 2023 class. A seven-time Pro Bowler and four-time All-Pro, he remains revered in Foxboro, following comments from current Patriots assistants.

“Well-deserved," said ex-teammate and Patriots linebackers coach Jerod Mayo. "(He was) one of those guys that you tell them, ‘Look, we want you to shut this guy down,’ and he’s going to get it done. A true professional, very smart player, very savvy. Would study, study, study his individual matchups and was always prepared to play. So congratulations to him.”

Steve Belichick echoed those same thoughts in a similar interview. Revis joined the team near the start of Belichick's career and left a lasting impression.

“I learned a lot from him in terms of preparation, practice habits and just his study of the game, how he thinks,” Belichick said. “I’ve been very fortunate to be around a bunch of good players, but specifically just more recently with him and Steph Gilmore.

“Being able to be around those two guys, they’re obviously amazing players but their approaches to the game and just how they operate on a day-to-day basis, taking care of their bodies and stuff like that. I was very fortunate to be around those guys. Congratulations to him and his big moment.”

"When you watch (Christian Gonzalez) go up against (DeVante Parker), it's like two heavyweight fighters." -- wide receivers coach Ross Douglas on recent Patriots practices.