The victory, the Legends' fifth in a row and 12th in 14 games, got them to .500 (16-16) for the first time in the second half since they were 2-2 and kept them two games behind first-place Rome in the South Atlantic League Southern Division.
Augusta broke a 1-1 tie in the eighth on Shawn Payne's run-scoring triple to center. Payne continued home on center fielder Justin Gominsky's error to make it 3-1.
The Legends came right back with a pair of runs in the bottom of the eighth. Ryan McCurdy led off with a walk and was replaced by pinch runner Ruben Sosa. Sosa moved to third on Delino DeShields Jr.'s single to left and DeShields moved to second on the throw. Nolan Fontana got Sosa home with a groundout and Zach Johnson tied it with a line-drive single to left.
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Mike Kvasnicka led off the bottom of the ninth for the Legends with a single, and Gominsky bunted him to second. After Jordan Scott walked, Alvarez delivered the winning hit.