The homer, in the top of the third, was Johnson's 13th this season, and the single helped Atlanta increase its early lead to 6-1 in the top of the fourth.
Four players had one RBI, and four had two hits for the Braves, who have split their last four games.
The winner was Ron Mahay (1-0), while closer Bob Wickman -- who had been thought to be headed back to Atlanta for an MRI on his right arm -- recorded his 19th save.
The loser was starter Adam Eaton (9-8).
Ray Liotta sues skin care company over use of likeness
Boston schools pull out free condoms over wrapping complaints