On May 23, 1875, the Reds played the Westerns of Keokuk at the Compton Avenue Park, coming away with a 7-1 victory on the strength of Joe Blong's two hitter. This game is not considered an "official" NA game for two reasons.
First, the game was played on a Sunday and, under NA rules, championship games could not be played on the Sabbath. Second, and more interestingly, the game was played under the "ten men-ten inning rule". This tenth man, I assume, was a type of rover and the position was listed in the box score as "r.s." And to state the obvious, a game played under these rules lasted ten innings rather than the normal nine. The Globe-Democrat wrote that this was the first time a baseball game had been played in St. Louis under these rules.
The Reds' rover that day was Charlie Sweasy and in Sweasy's normal spot at second was someone named "Fox". The Globe's coverage of this game is the only mention of Fox playing with the Reds.
An official championship game between the two teams had been called off the day before because of "the forbidding aspect of the weather". With the Westerns leading 4-1 in the fourth inning, the rains came "in torrents", forcing the cancellation of the game.
Since the Westerns had two games scheduled with the Brown Stockings and were going to be in St. Louis for the rest of the week, it is unclear why the Reds and Westerns didn't make up the championship game and chose instead to play an exhibition.