Will Pollard scored all of the Tomcats' runs, reaching base on an error, walk and a single. Brad Verhoeven and Nick Brooks, both had a single and one base on balls.
Pitcher Mason Newell picked up the win in relief of Zach Banks, who worked the first five innings of the seven inning game.
In game two, the Tomcats exploded for five runs in the first inning and six more in the fifth, to win in a mercy.
Fishback was two-for-two and had two walks to first base. Alex Pettipiece batted two-for-three and scored twice.
Pollard and Alex Liem, each had a single, walk and scored two runs.
Brett Reid took the win, striking out five batters, with Jake Haak coming in for the fifth inning and striking out the side.
The 'Cats, with a 5-2 record in league action, visit Kitchener Tuesday and Brantford on Thursday.
St. Thomas hosts the Ontario Baseball Association 22U provincial tournament this coming weekend. The Tomcats face Newmarket in their opening game, Friday, 5:30 p.m. at Emslie.