"It's been a whirlwind," Mack said.
From holding out of camp with the Oakland Raiders to signing the richest contract for a defensive player in NFL history, Mack hardly had time to notice much upon arriving Sunday in Chicago at Halas Hall -- like the billboard that had sprung up already overnight welcoming him to the city.
Trades haven't traditionally been the Bears' forte, as the Jay Cutler and Rick Mirer deals showed.
A franchise mired in the depths of the NFC North for four years has been building hope since last season ended. And the feeling by Bears general manager Ryan Pace and head coach Matt Nagy is that Mack can be the last big change to make the Bears relevant again in November, let alone December.
"I've always thought of myself as the best defensive player in the league and I want to play like the best defensive player in the league," Mack said. "I want to be the best at what I do, and that's just me. That's what comes with Mack."
The $90 million guaranteed in his $141 million contract says he has to be what the Bears hope. He has set a bar for defensive players around the league in future negotiations.
The Bears paid a steep price for Mack in the form of first-round draft picks in 2019 and 2020, a third-rounder in 2020 and a sixth-rounder in 2019. In return, they received Mack and second- and fifth-round picks in 2020. The fifth-round choice is conditional.
Pace has repeatedly stressed the need to build through the draft, yet Mack made him forget this creed. Pace insists the future is not being sacrificed even if it looks this way.
"I think it's his youth, the position he plays and it's the dynamic player that he is," Pace said. "It's kind of the rare moment that this type of player becomes available and when that happens, going in and getting that guy."
So, suddenly the Bears have a superstar defender after building a top-10 defense last year under coordinator Vic Fangio without well-established playmakers.
Nagy has a team possessing greater speed to the ball with Mack and first-round draft pick, linebacker Roquan Smith.
The end result is greater pressure on Nagy's own offense simply to carry its load.
"The defense obviously has been very productive in regards to the last couple years and now you add a great piece like this, it helps out," Nagy said. "So, for our team offensively, there's questions. There's questions of where we're going to be at and we won't know that until we continue to grow week by week."
The whole trade materialized almost overnight, although Pace said he talked with Nagy about the possibility of pursuing Mack at the outset of training camp. When it happened, it occurred so fast that Mack had no time to really thank former teammates in Oakland.
"You get texts from your teammates -- well, your old teammate," Mack said. "Yeah, you can say goodbye that way. You really don't have that chance."
The Bears cut center Hroniss Grasu to put Mack on the roster, and begin the process of fitting Mack in at Monday's practice. They will watch closely as he works to see if he can face Aaron Rodgers and Green Bay on Sunday night at Lambeau Field in the opener. They want to avoid a hamstring injury, like Smith suffered after his 29-day holdout to start camp.
"We'll see where he's at and hopefully he's able to go out there and play well, but it will be more of a day-by-day thing than anything," Nagy said.
Facing Rodgers twice a season is something Mack looks forward to experiencing.
"That's exciting," Mack said. "You want to go against the best. I feel like he's one of the best in the game."
With the bold trade, the Bears are banking on the opposition saying the same about Mack.