Sullivan faced two batters over the minimum, allowing a pair of hits while striking out five. He threw just 50 pitches. The Captains' pitchers were nearly as good, retiring the final 16 TinCaps hitters in order.
Fort Wayne scored in the top of the first against Captains RHP Trey Haley. Danny Payne led off the game with a walk, stole second and third bases, then scored on a sacrifice fly by Jeudy Valdez.
The TinCaps had a chance to expand the lead, but couldn't capitalize. Nate Freiman led off the second inning with a double, but he never moved from that point.
Fort Wayne did not have a batter reach base after the fourth inning; Lake County RHPs Jeremy Johnson and Tyler Sturdevant combined to retire the final 16 batters of the game.
The Captains threatened with leadoff hits late in the game. Casey Frawley roped a leadoff double in the seventh but was stranded. Ben Carlson singled to lead off the eighth but did not score.
Sullivan (7-3) picked up the win; Haley (4-4) was saddled with the loss. Schumacher notched his 19th save.
Fort Wayne upped its record to 8-7 in the half, 44-41 for the season. Lake County fell to 8-7 in the second half, 39-45 for the year.
The TinCaps open a three-game series against the South Bend Silver Hawks (Class-A Arizona Diamondbacks) Saturday at 7:05 p.m. at Parkview Field. Fort Wayne LHP Mike Watt (4-4) makes the start against Captains RHP Andrew Wolcott (0-1).