Half of each team's first 12 games come against the other, beginning Friday with Washington's home opener.
''I really wouldn't say we're rivals, as much as just two good teams,'' Braves shortstop Andrelton Simmons said. ''But it means a little more when we play them. We respect them, and I think they respect us.''
The Nationals led the majors with 98 wins in 2012, but they finished 10 games behind the Braves in the division in 2013.
Two major problems for the Nationals a year ago were a poor start and an inability to beat the Braves, who won the clubs' season series 13-6. After their three-game series this weekend, the teams play three more at Atlanta a week later. But then they won't face off again until June.
''Obviously, there's a history with us and the Braves with what happened last year, but it's a new year,'' Nationals reliever Tyler Clippard said.
''Once the season starts, any time you play an inter-division team, you want to win those games,'' Clippard said. ''If you're playing well within your division, you're going to have a better opportunity to win your division. ... When Atlanta comes to town, we'll be looking forward to beating up on them a little bit.''
The Nationals are 3-0 after sweeping a series at the New York Mets, capped by an 8-2 victory Thursday. That finale was supposed to be started for Washington by right-hander Jordan Zimmermann, a 19-game winner last season, but he developed a fever overnight and was throwing up. So Zimmermann was replaced Thursday by Tanner Roark, who had been scheduled to start Friday against the Braves.
Nationals manager Matt Williams said Zimmermann would start Friday if he's feeling better - and if not, a series of relievers would be used. Either way, Williams did not plan to decide until a few hours before the game.
''We don't want to send him out there with him being really sick,'' Williams said, ''so we'll see how that goes in the morning.''
Early as it is in his first season as a manager, Williams already has faced plenty of key decisions and adjustments.
Right-hander Doug Fister was acquired via offseason trade from Detroit to be the No. 4 starter - and, therefore, on the mound Friday - but he is on the disabled list with a strained muscle on the right side of his upper back. Catcher Wilson Ramos, the cleanup hitter on opening day, is expected miss at least a month after having surgery Wednesday for a broken bone in his left hand. Left fielder Harper had a scary collision in Game 1 and said he passed concussion tests.
The Braves, who went 2-1 in their opening series at the Milwaukee Brewers, have their own problems, particularly when it comes to pitchers.
Kris Medlen and Brandon Beachy got season-ending elbow injuries. Mike Minor (returning from a sore shoulder), Gavin Floyd (coming off 2013 elbow surgery) and Ervin Santana (a late free-agent signing) are prepping in the minors. David Hale is scheduled to make his sixth career start Friday.
''We got off to a good start against the Nationals last year, and we want to do it again,'' Braves outfielder Heyward said. ''We know they're a good team and I think they feel the same about us. Nothing has really changed. We've had some great games and I'm sure we will again this year. It's always exiting when we play them.''
AP Sports Writer Ronald Blum in New York, and freelancers Carl Kotala in Viera, Fla., and Guy Curtright in Kissimmee, Fla., contributed to this report.
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