Delta had beaten Roaring Fork, in Carbondale, 7-3, in a contest played April 12. Last week's encounter, in Delta, swung the opposite way with the Rams scoring a 2-1 overtime win against the Panthers.
Neither team scored in the opening half and Roaring Fork took a lead late in the second half on a lofted kick that was too high for Delta keeper Joslyn Carpenter.
The Panthers stepped up their pressure defense and got some luck on a penalty kick from 20-plus yards to score a tying goal by senior Missa Webb with less than two minutes remaining in regulation play.
Roaring Fork had the luck in the extra period when a corner kick was deflected into the net for the game-winner.
The Rams, second in 3A WSL standings, moved to 5-2 and 8-7 while Delta's record slipped to 4-3 and 7-7.
Delta finished fourth in league play.
Berths in post-season play indicate the Panthers have made the post-season field of 32 at No. 26 and will play No. 7 Peak to Peak (10-5) in first round action on May 8. The winner plays either No. 10 St. Mary's (11-4) or No. 23 The Academy (8-7-0) May 11.
Aspen (6), Roaring Fork (19), Coal Ridge (25) and Basalt (29) also made the playoffs.