The 25-year-old, who spent three full seasons with the Pilgrims, is poised to join Blue Square Bet Premier side Nuneaton Town.
United boss Jason Lee told bufc.co.uk: "We wish Danny well. He is stepping up a division and we cannot stand in his way. We expected the move in all honesty and talks are under way with targets to replace him."
Everybody at Boston United would like to thank the player for his sterling service over the last three seasons and wish him well for the future.