South Bend leads the TinCaps 1-0 after three innings Thursday at Parkview Field.
Fort Wayne has been held without a hit by South Bend starter Blake Perry.
South Bend took a 1-0 lead in the first when Ronnie Freeman doubled, went to third on a wild pitch and scored after Alex Glenn reached on an infield single.
Fort Wayne (43-26 in first half) finished one game behind South Bend (44-25 in first half) for the division title with the TinCaps getting the wild card playoff berth.
The TinCaps are 0-6 this year against South Bend.