Slazenger seconds suffered only their third defeat of the season to a young, skilful Rotherham outfit.
Slazenger got off to a dreadful start, conceding a goal with barely a minute played. And by the quarter-hour mark the hosts were 3-0 down. The Horbury men hauled themselves back into the game but were unable to crack the defensive deadlock before half-time.
Slazenger started the second half on top and pegged a goal back through Alec Gilston, only for Rotherham to restore their three-goal cushion.
Credit to Slazenger, however, who continued to work hard and were rewarded with a second goal for veteran Simon Hurley.
Man of the match went to Ben Garside whose fighting spirit was an example to the rest of the team.