Last month before the Bears started their offseason program, Mooney spent a few weeks in Atlanta working out with Fields and staying at his home.
"[It was] very beneficial," Mooney said Thursday as the Bears concluded their voluntary three-day minicamp. "We grew on the field and off the field, learned [about] each other more than what we knew of each other.
"I was staying with him at the time, so [we were] just sitting in the house whenever we were done working out just talking, communicating just about life and football and what we were expecting throughout this season."
Because they hadn't yet received a new Bears playbook, Mooney and Fields didn't work on any specific plays, focusing instead on honing their timing.
"We didn't know the scheme of what we were running or any of the routes, so we were kind of just winging it and just doing what we could do," Mooney said. "But [it was] very beneficial; [we] grew a lot."
Mooney noticed that Fields was putting more touch on his passes than he did last season as a rookie.
"Last year he threw the ball extremely hard," Mooney said. "He was eager to get the ball out of his hands. He knew his arm was strong. He's grown to get some touch on it. It's a nice ball, a very nice ball. I know when we were in Atlanta, he was throwing really, really great. We were talking smack to each other. Then there was one day that he was throwing the ball extremely well and I was like, 'This is my last time complimenting you, but good-ass ball.'"
Bears coach Matt Eberflus predicted that the cohesiveness that Fields and Mooney worked on in Atlanta will manifest itself at some point in a game.
"There will be a moment," Eberflus said. "I don't know when that's going to be, but you'll be able to see it. The timing and the rhythm and the consistency of it, that's what you'll be able to see.
"What they did in Atlanta together, that's great. That was a start. And that's where they are now because of that; they're at a higher spot now because they did that work. It's just like this offseason; guys will be at a higher spot in training camp if we put in the work now. That's the main goal for everybody and every unit, and you can see that with those guys."
A fifth-round pick in the 2019 draft out of Tulane, Mooney has far exceeded expectations since entering the league. Last year he recorded the 18th 1,000-yard receiving campaign in franchise history, and his 142 career receptions are the most by a Bears player in his first two NFL seasons.
Determined to perform at an even higher level this year, Mooney has been working to improve his conditioning.
"I want to be able to play six quarters," he said. "I want to be able to play faster than anybody else on the field, not get tired.
"Antonio Brown, he runs in and out of the huddle. He's never tired. Cooper Kupp in the Super Bowl, that last drive he got the ball maybe 6-7 times. In the end zone, he was dead tired. But you couldn't see that he was tired at all catching the ball and going back to the huddle.
"Me being able to do that, and be consistent with that and maybe the targets are going up even more this year, so I have to be able to take that on and just not be tired."
To that end, Mooney has incorporated a lot more running into his offseason training regimen—on the field and even on the street in his neighborhood.
"I do more miles and a lot of short-timing things," he said. "Just anything off the wall, anything I can challenge myself to do."
“I want to be able to play six quarters. I want to be able to play faster than anybody else on the field, not get tired.” Bears WR Darnell Mooney on improving his conditioning
Always driven to succeed, Mooney will always be motivated by having to wait until pick No. 173 to hear his name called in the draft.
"I know what I want out of my life and I know what I want out of this league," Mooney said. "[I was] disrespected as a fifth-rounder when I was picked … At the end of the day, I will get my respect and I'm going to keep going until I get my respect. Even when I do get my respect, I'm still going to keep going."