Atlanta designated Thompson for assignment Monday.
He'll cede his spot on the 40-man roster to outfielder Eddie Rosario, whom Atlanta signed to a one-year contract. The 31-year-old Thompson previously made two appearances out of the big-league bullpen earlier this month but had struggled since returning to Triple-A Gwinnett on April 16, giving up six runs (three earned) on seven hits and three walks over 4.1 innings.