FRISCO, Texas – Amari Cooper's on-field persona was formed before he played his first game as a kid.

“I overheard one of my friends say, ‘If Amari scores, I bet he’s real happy and he’ll get real excited,’” Cooper said. “I just so happened to score, and since I heard him say that, I was like, ‘Nah, I’m not going to get really excited.’ And for some reason, that felt like the right thing to do. I been the same way since.”

In a league filled with diva wide receivers, Cooper is the anti-diva. He drives a nice BMW and dresses impeccably, but he thinks before he speaks. Emotions do not spill out of him. He is careful not to celebrate too much.

Slowly, the low-key Cooper has become more comfortable in expressing himself, coming from the disappointing end of his time with the Oakland Raiders to the high of a playoff run with the Dallas Cowboys that he hopes continues in Saturday’s divisional round at the Los Angeles Rams (8:15 p.m. ET, Fox).

“I used to feel like, ‘Why are those guys so excited if they know they’re great players,” Cooper said inside a quiet Cowboys locker room before afternoon meetings on Wednesday. “I mean that should be what they expect to go out and do. That’s why I never used to celebrate, because I expected to do that. I expect to do more, and if I scored a touchdown, I’d look at it like that’s not much. I can score three or four times. But recently, I had a change in views.

“A lot of guys go through ups and downs in their careers, and sometimes those downs are like horrific and they can really change you. A lot. And so when you go out there and do something like score a touchdown and have a good game, you appreciate it so much more when you’ve been through those valleys in life. I can see why guys really celebrate and actually appreciate the time and have fun in the moment. But I couldn’t before.”

After a touchdown against the Washington Redskins on Thanksgiving, he imitated the free throw of Philadelphia 76ers guard Markelle Fultz.

“Nobody knew I was going to do it,” Cooper said, “but the guys are pretty smart, so I knew they would catch on eventually when I told them to line up.”

After one touchdown against the Philadelphia Eagles, he paid homage to Terrell Owens standing on the star, spreading his arms wide.

“That was subconscious,” he said.

While there have been more emotions, there have been no negative triggers. In that signature game against the Eagles when Cooper caught 10 passes for 217 yards and three touchdowns, the closest he came to showing frustration was sagging his shoulders when Dak Prescott called for him to run another stop route.

“When I broke the huddle, I was kind of mad and I was like, ‘Dak, come on,’” Cooper said after the game. “And he was like, ‘Just run it, bro.’”

At the line of scrimmage, Prescott changed the route, and they connected for a touchdown.

But Cooper's complaint did not rise above a “come on.”

Oh, he could demand the ball. He could call out the game plans. He could walk up and down the sideline gesturing wildly. During the week, he could complain to the coaches about a lack of opportunities. Maybe he could fire a ball at Prescott the way Antonio Brown reportedly did to Ben Roethlisberger going into the final week of the regular season.

Cooper does none of it.

“That’s Amari. Yeah, he’s always been the same way,” said E.J. Hilliard, his quarterback at Miami Northwestern during his senior year in high school. “I could probably count on one hand, maybe two times I saw him get emotional as far as showing his excitement. He’s like the opposite of a No. 1 star receiver like you would expect. You expect him to say, ‘I’m open, throw me the ball,’ but he was never like that.”

Well, not never. There was one time.

Hilliard remembers it was against Coral Gables. Northwestern was up three scores, so the game was well in hand; but after a third-and-long pass didn’t go Cooper’s way, he went to Hilliard.

“He was like, ‘Hey, I think I was open there. I don’t know, maybe I wasn’t in your progression or maybe there was some pressure. So, if we got a chance to go back to it again, just keep that reminder,’” Hilliard remembered.

E.J. Hilliard (12) said Amari Cooper rarely got emotional during their days at Miami Northwestern High School, unless you consider Cooper questioning Hilliard's checkdown progression to be emotional. Courtesy E.J. Hilliard

That doesn’t quite roll off the tongue like Keyshawn Johnson’s book title, "Just Give Me The Damn Ball," does it?

Colorful wide receivers dot the history of the Cowboys.

Drew Pearson, the Original No. 88, had a flare to his game. When Michael Irvin walked into a room, everybody knew The Playmaker was there. Dez Bryant had an oversize charisma that he carried on and off the field. For three seasons in Dallas, Owens might have topped them all.

Conversely, Cooper recently slipped out of the locker room unnoticed after he had a conversation with practice squad wide receiver Reggie Davis.

“He just wants to play football,” said Teddy Bridgewater, Cooper's first quarterback at Miami Northwestern and now Drew Brees’ backup with the New Orleans Saints. “Shows up, and he’s not gonna make a scene or anything. He’s a grinder, and he’s serious about his craft.”

On Wednesday, Cooper stood on top of a riser in front of his locker. It wasn’t to draw attention to himself. It was to accommodate the crush of media on hand for the Cowboys’ playoff run.

"He just wants to play football. Shows up, and he's not gonna make a scene or anything. He's a grinder, and he's serious about his craft." Saints QB Teddy Bridgewater, Cooper's first QB in high school

“I don’t really have a shell,” Cooper said. “I’m really not as quiet as people think I am. I’m really not that quiet. But I don’t know, I would say I’m more observant.”

The acquisition of Cooper changed the Cowboys' season. With a 3-4 record after a loss to Washington, the Cowboys gave up their 2019 first-round pick to the Raiders for Cooper. In nine regular-season games for Dallas, Cooper caught 53 passes for 725 yards and six touchdowns.

“Ultimately, what matters most is how you prepare and how you go play,” Cowboys coach Jason Garrett said. “Different players at every position have different personalities. Emmitt Smith was a very impactful player in this organization for a long time and not someone who was very vocal -- each and every day kind of came and went to work, practiced and certainly played at a very high level. Been around a lot of different personalities, like we all have, and the biggest thing is you want guys to be themselves and go about it the right way.”

Offensive coordinator Scott Linehan was around Randy Moss for three seasons with the Minnesota Vikings. He called plays for the Detroit Lions when Calvin Johnson caught 122 passes for an NFL-record 1,964 yards in 2012; at 6-foot-5 and 237 pounds, Johnson had a presence.

“Calvin was just this massive guy,” Linehan said. “Calvin kind of spoke with his enormous physique. But Calvin, he was probably similar [to Cooper] in a lot of ways. Maybe a little quieter. You didn’t hear him coming, that type of thing. But so, hey, everybody is who they are.

"I love all the receivers I’ve been around and just appreciate their personalities, these elite-type players. There’s something about them that’s different. He’s real similar in a lot of ways.”

Most Impactful Receivers After A Trade Amari Cooper has the most receiving yards per game after changing teams during a season in the Super Bowl era with a minimum of five games. Year Player New Team Receiving yards/game 2018 Amari Cooper Cowboys 80.6 1981 Wes Chandler Chargers 71.4 2018 Josh Gordon Patriots 70.1 2009 Chris Chambers Chiefs 67.6 Source: Elias Sports Bureau

At 6-foot-1 and 210 pounds, Cooper might have something of an average build, but not an average game.

“I tell people all the time, when he first got [to Miami Northwestern], this was when Percy Harvin had just left Florida, and I was like, ‘Man, this guy is gonna be the next Percy Harvin,’ because he was only like 5-8 when he first got there, but he could run,” Bridgewater said. “So, we ran spread offense, motions, jet sweeps. Came back the next year he was about 5-10, and it was like, ‘Hold on. I don’t know about Percy Harvin anymore.’ Then the next year he was like 6-foot, and it was like, ‘Man, this kid is like A.J. Green or Julio Jones.’

“So he’s a guy that continued to just grow physically and mentally, and it’s exciting to see him perform the way he is right now.”

Projecting Cooper’s nine-game stats over a full season, he would have produced on the field like an Irvin, Bryant or Owens did, with 94 receptions, 1,289 yards and 11 touchdowns. He will never become Irvin, Bryant or Owens in terms of personality and verve, but he’s getting there.

“Amari’s starting to open up a little bit,” Prescott said. “He’s starting to talk a little bit more. I don’t know if it’s winning these playoffs or what. We know that we need his leadership, him be a little bit more vocal or whatever it may be. He’s opening up.”

ESPN New Orleans Saints reporter Mike Triplett contributed.