FSV had gone into the game in excellent form and could have leapfrogged their hosts with a win, but Benno Möhlmann's charges were stunned by a first-half flurry at the Fritz Walter Stadion, at the end of which they trailed 4-0.
Albert Bunjaku opened the scoring when he tapped in from Mohamadou Idrissou's centre on 27 minutes, before a trio of strikes before the break put the Red Devils in full command. Marc Torrejon and substitute Benjamin Köhler each increased the advantage, before Bunjaku grabbed his second in first-half injury time.
Edmond Kapllani pulled one back for FSV late on, but it was too little, too late for the visitors, who are now five points adrift of Lautern with only two games remaining. The hosts, meanwhile, increase their advantage over fourth-placed 1. FC Köln, who lost to VfL Bochum on Saturday, to four points and remain in pole position to secure the promotion play-off spot.
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