The visiting Rattlers battled from behind in the first half, but they managed a 2-2 tie at the break.
Fond du Lac scored two straight goals in the second half to take command.
“Our last game, our offense sputtered,” said Rattlers coach Grant McNall. “I decided to go with a different lineup, and it didn’t work out.”
Not only were the Rattlers saddled their first league loss, starters Nick Miller and Mike Schram went down with injuries. Miller has a severely sprained ankle, and Schram received 11 stitches in his knee after being cleated.
UW-Rock (2-1, 3-2-1) travels Wednesday to UW-Sheboygan.
UW-Rock County 2 1—3
UW-Fond du Lac 2 2—4
UF—Brandon Blake (Tyler Smeth), 4:00. UR—James Baines (penalty kick). UF—Bryce Bertelt (Blake), 9:00. UR—Grant Jahns (Tyler O’Rourke), 33:00.
UF—Bertelt (Blake), 49:00. UF—Smeth, 52:00. UR—Jahns (Joe Benson), 80:00.
Saves—Jose Montero (UR) 4, Matthew Brey (UF) 13.