T.P. Sullivan, who managed the St. Louis Base-ball Club last year, has signed a contract to manage the new Union Club that has been organized in [St. Louis.] Henry N. Lucas, the President of that organization, has sent Sullivan on a roving commission with power to engage any player whose services would be likely to strengthen the new club. Sullivan will visit Pittsburg, New York, Cleveland, and other League and association cities. The club needs another first-class pitcher and two catchers, and Sullivan will secure these at any cost.
-New York Times, December 28, 1883
T.P. Sullivan says the report that he has signed with the Lucas Club as manager is incorrect, and he wishes it denied.
-St. Louis Globe-Democrat, December 30, 1883
We know that Sullivan was working with the Maroons as early as late October 1883. In the first week of November, it was mentioned that he would be the new manager of the club and, at the end of November, he was signing players for the club. But in late December 1883, according to his own words, he had still not agreed to manage the Maroons. He may have still had ties to the Richmond club but I thought that had all been settled in early November.
Regardless, we know that at some point Sullivan will agree to manage the club.