The league said Vizcaino tested positive for the anabolic steroid Stanozolol. He will be suspended without pay.
Jeff Passan of Yahoo Sports, who first reported the suspension, reports that Vizcaino "had thrown significantly harder this spring than he had in recent seasons."
The 24-year-old was optioned to Triple-A Gwinnett by Atlanta on Monday. He will serve the suspension there.
The Braves acquired Vizcaino from the Chicago Cubs in a trade last November. He made his MLB debut in 2011 and was once rated among the Top 100 prospects in baseball.
In 2012, Vizcaino underwent Tommy John surgery and did not pitch again in the majors until September 2014. He had four strikeouts in five innings and gave up three runs for the Cubs last season.
- Molly Geary