The Dragons, who held a one-game lead in the wildcard race entering the series, have lost eight straight road games.
They have 10 games remaining to play including three against South Bend, all in Dayton, and may need to win them all to reach the post-season.
Dayton scored just nine runs in the four games in the series and not more than three in any game.
The Dragons picked up the lead in the third inning. With one out, Kevyn Feiner singled to center and went to second when Josh Fellhauer's sacrifice bunt was mishandled by third baseman Justin Parker. Feiner and Fellhauer pulled off a double steal and Feiner scored from third on Cody Puckett's sacrifice fly to right to make it 1-0.
But South Bend scored four runs in the fifth inning against Dragons starting pitcher Mark Serrano (2-1) to take a commanding lead. With one out, six consecutive batters reached safely on three hits, a walk, a hit batsman, and an error on Dragons second baseman Cody Puckett. Rossmel Perez's two-run single brought in the first two runs and the last two scored on Puckett's error as the Silver Hawks took a 4-1 lead.
Dayton scored an unearned run in the eighth inning when Miguel Rojas, who had reached on a walk, scored from second on an error to make it 4-2. But with two men on base and two outs, Carlos Mendez grounded out to third to end the threat.
In the ninth, Humberto Sosa singled to lead off the inning and with one out, Mike Konstanty drew a walk to put the tying runs on base. But South Bend's Victor Capellan struck out Rojas and Feiner to end the game.
The Dragons were 0 for 6 with runners in scoring position after going 1 for 11 on Wednesday night.
The Dragons return home Friday to open a four-game series at 7:00 p.m. against the Lansing Lugnuts at Fifth Third Field.
Justin Walker (0-1, 2.40) will start for Dayton. The Dragons are 11-5 against Lansing this season.