When defensive lineman Joe Gaziano rumbled into the end zone with an intercepted pass, Bosa and Mack sprang to their feet to join in celebration then returned to the sideline, stood hip to hip and resumed conversation.
"I just love to have a guy like that to lean on, ask questions, whether it's about football or just life," Bosa said about Mack, whom the Chargers acquired via trade with the Chicago Bears in March.
Through two weeks of training camp, Bosa and Mack have appeared inseparable -- whether meeting in the backfield, on the sideline or at the film room.
"He's a fun dude," Mack said about Bosa. "But when it comes down to work, we work."
In Brandon Staley's first season as coach in 2021, the Chargers finished 9-8, third in the AFC West, and missed the playoffs for a third consecutive season.
Despite being under the direction of a defensive-minded coach -- as the Los Angeles Rams' defensive coordinator in 2020, Staley's unit ranked atop the NFL -- the defense turned in a subpar performance, ranking No. 26 in efficiency and No. 29 in points allowed, with opponents scoring an average of 27 points per game.
But after an offseason headlined by a personnel overhaul to better fit Staley's scheme -- including the additions of Mack, cornerback J.C. Jackson, linebacker Kyle Van Noy and defensive linemen Sebastian Joseph-Day and Austin Johnson -- the unit is expected to excel, especially with the return of Bosa and All-Pro safety Derwin James Jr., who remains a training camp hold-in while awaiting a contract extension.
"You have to be a complete defense, a team at all three levels that plays together. You have to play with toughness ... discipline ... physicality," Staley said. "We have to come together in training camp and really create and crystallize that identity."
It's Bosa and Mack who are expected to lead the way.
Over the past five seasons, they each have ranked in the top four in total defensive pressures. They both have 12 strip sacks in the past five seasons, tied for sixth in the league, and have a combined 134.5 career sacks.
Now on the same team, Bosa and Mack form arguably one of the top pass-rushing duos in the NFL.
"There are a lot of things that are going on between them that not many people would understand," Staley said. "To see the game through two superstars' lenses like that, two of the top players at their position in the last several years, to be teaming up and sharing their stories and what they see, it's really special."
Both veterans have somewhat eased into training camp, with each being -- by design -- limited in their 11-on-11 participation and taking some rest days. But that hasn't slowed them from learning each other's game.
Along with spending time together on the field -- "Half the time, it's just throwing ideas at each other, and the other half of the time, it's just shooting the stuff with each other and just talking about life," Bosa described -- they've also taken to the film room, studying tape of pass-rushers such as Nick Bosa, Chandler Jones and Myles Garrett.
"When we turn on the film, it's just -- I don't know, automatically, we kind of see the same things, but also we see different things," Mack said. "It's kind of like a yin and yang in the sense of understanding the game."
Perhaps also a yin and yang in their approach.
Mack described Joey Bosa as a technical and methodical rusher, while labeling himself as the opposite.
"I kind of take what you give me," Mack said. "I'm not paying attention too much to the tackle; I pay more attention to the quarterback when I rush."
It's not just the defensive front, or even the defense, that is feeling the Bosa-Mack effect.
"I've never played with a pass rush like that," said Jackson, who signed a five-year, $82.5 million contract in free agency after playing four seasons with the New England Patriots. "I believe I can make more turnovers having those two guys going at the quarterback."
Jackson leads the NFL in interceptions since 2018 with 25.
"For us to be able to face those guys every day makes us better," quarterback Justin Herbert said.
"It's good that we're going against them out here," veteran center Corey Linsley said. "They can do it all. They're technicians."
Bosa, the No. 3 overall draft pick in 2016, recently admitted he wasn't sure that he would have previously embraced a partnership with Mack, the fifth overall pick in 2014.
"As a rookie or a few years into my career, it would have been a negative almost in a way where I'm too in my head, too hypercompetitive," said Bosa, a four-time Pro-Bowl selection.
But now, at 27 years old and with six seasons of experience, the partnership could be what Bosa and the Chargers need to propel them into the playoffs.
"The competition, having an elite guy like that to look at and be like -- just keep you on your toes," Bosa said. "It's just great to have that guy to compete with and lean on."
A fresh start in L.A., coupled by a reunion with Staley -- his former position coach in Chicago -- also could benefit the 31-year-old Mack, who was limited to seven games in 2021 because of season-ending foot surgery.
"My expectations for myself are always high," said Mack, who produced six sacks in seven games last season. "I'm not going to display or tell what they are, but I expect you guys to be able to see it when I touch the field."