B.J. Upton, Justin Upton and Jason Heyward make up Atlanta’s revamped outfield. (Scott Cunningham/GETTY IMAGES)

In the eighth inning of a game Sunday, a pinch hitter for the Chicago Cubs named Dave Sappelt drilled a ball to deep center at Turner Field, a shot destined at least for the warning track, maybe further. Justin Upton, watching from left field, thought nothing of it. Jason Heyward, looking on from right, was scarcely concerned. And B.J. Upton started to run.

“I’ve been around him so long, it always looks like he’s not running, but he’s covering some ground,” said Justin Upton, B.J.’s younger brother. “He’s just long and lean. Running’s easy for him.”

The season is young, and evaluations will be made over time. But when the Atlanta Braves signed B.J. Upton as a free agent this offseason, then traded with Arizona for Justin, a determination was made, both internally and across baseball: The Braves’ outfield is where balls to the gap become easy outs, where shots to the warning track look, in the scorebook, like popups.

“I feel like most of the balls that stay in the yard, that aren’t going off the wall,” Heyward said, “I feel like all three of us have an opportunity to catch them.”

When the Braves come to bat in the first inning of Friday night’s series-opening game at Nationals Park, the Washington Nationals will trot out Bryce Harper to left field, Denard Span to center and Jayson Werth to right. And over the weekend — as the two favorites in the National League East play the first of six intriguing series against each other, with the Braves already on a six-game winning streak — Nationals Park could serve as the stage to debate which outfield is the NL’s best.

“They have a very good outfield, and they’re good baseball players,” Braves General Manager Frank Wren said of the Nationals. “That’s what makes them such a tough, competitive ballclub, and I think we have players like that, too.”

The Nationals’ major offseason desire was to cure what had long ailed them — a lack of a leadoff hitter and center fielder, and trading top prospect Alex Meyer for Span addressed that need. Span is off to a fine start, with a .475 on-base percentage entering Friday’s game.

But it’s also not a stretch to think Span could have ended up in Atlanta, where the Braves allowed Michael Bourn to walk as a free agent.

“We were all talking to the same players,” Wren said. “We were all talking to the same teams.”

On Nov. 29, the day the Nationals traded for Span, the Braves signed B.J. Upton to a five-year, $72.25 million deal. But it wasn’t until nearly two months later the Braves traded Martin Prado — a former all-star and one of their best players — top pitching prospect Randall Delgado and three minor leaguers to Arizona for Justin Upton and third baseman Chris Johnson.

“We knew it was a special group,” Wren said.

Justin Upton, 25 and the top pick in the 2005 draft, entered Thursday’s games leading the National League with an on base-plus-slugging percentage of 1.365, and he has six home runs in his first nine games. B.J. Upton, 28 and the second overall pick by Tampa Bay in the 2002 draft, is off to a slow start, hitting just .103, slugging just .207.

The Washington Post’s Mike Wise offers his extra points about Bryce Harper and his future professional baseball career. (Post Sports Live)

But he and his brother already have a signature moment as teammates. Last Saturday, the Braves trailed the Cubs by a run in the bottom of the ninth. B.J. led off with a homer to tie it, and an out later, Justin won it with a shot of his own — becoming the first brothers to homer in the same inning in major league history.

Wren said watching the Uptons’ parents high-five Braves fans in the club seats behind home plate was “one of the coolest experiences” he has had. But for the rest of the league, that cool experience demonstrated the potential of Atlanta’s dynamic outfield.

“It’s two more guys who can beat you any kind of way — defense, offense, speed, throwing the ball, hitting home runs or hitting for average, running the bases,” said Heyward, an all-star in 2010 who’s still just 23. “It just takes some time — making sure everybody understands the terminology we’re going to use, understands who can get to what, and making sure you communicate. After that, when we have three guys who can get to almost everything, it makes it pretty easy.”

If there has been, traditionally, one knock against the Uptons and Heyward, it is for unrealized potential. After posting an .849 OPS as a rookie, Heyward dropped to .771 over the next two seasons. After becoming an MVP candidate in 2011 (31 homers, 88 RBI), Justin Upton’s production fell precipitously in 2012 (17 homers, 67 RBI). For all his promise, B.J. Upton’s career numbers are: .254 batting average, .335 on-base percentage and .420 slugging, and he developed a reputation — fairly or not — for an occasionally lackadaisical approach on defense.

Which brings us back to that ball in the eighth inning on Sunday. B.J. Upton’s gliding steps brought him under the ball smoothly at the warning track, an easy out.

“You’re thinking, ‘You got to get there,’ because he’s not running, he’s not running, he’s not running,” Braves Manager Fredi Gonzalez said. “And the next thing you know, he catches the ball. It’s amazing because you don’t think that he’s running, but he’s chewing up ground to catch that ball.”

That, Justin Upton said, is “100 percent” why some people believe his older brother doesn’t go all out.

“I don’t really care what people think,” B.J. Upton said. “I just roll with it.”

When last Sunday’s game was over, B.J. Upton dressed at his locker stall, with Justin one stall over and Heyward one beyond that — in this case, center, left and right fields, all in a row. Heyward let out a loud chuckle at something Justin said, and headed off to the shower, cleaning up for a road trip that would start with a sweep of the Marlins in Miami.

And when Justin Upton tried to walk away toward the bus, B.J. Upton reached up and grabbed him by the shoulder, stopping him. Justin’s purple shirt wasn’t properly covering his purple tie. B.J. stood up, fixed the collar, and Justin walked off, dapper again. It became clear once more: There may be no potential problem this Braves outfield can’t get its mitts on.