The Biscuits dropped their fourth straight game, 7-3 to the Jacksonville Suns on Sunday, and have watched their division lead evaporate.
Montgomery, which sported a four-game lead four games ago, is now tied with Jacksonville for first place in the Southern League's second-half South Division race. There are seven games remaining in the season.
Game 4 of the five-game Biscuits-Suns series will be at 7:05 p.m. Monday.
Jose Duarte's two-run single capped a four-run sixth inning that gave Jacksonville a 6-3 lead. Ben Lasater added a solo home run in the ninth. Kyle Jensen scored three times for the Suns, while Duarte finished with three RBIs.
Mayo Acosta hit a two-run homer in Montgomery's three-run fourth. He left in the sixth with an apparent ankle injury after a collision at home plate.