Thanks to the Vigo County Historical Society and Museum, we have identifications for the 1889 Terre Haute team photo. Most of these players are noticeably missing from Baseball-Reference's roster, which makes me doubt the roster almost entirely, as I have found little evidence to support some of these players in the contemporary newspapers (in an admittedly quick search). I did find a series of articles about the Terre Haute Hottentots online, one of which mentions numerous players on the roster.
(
https://indianamemory.contentdm.oclc.../vcpl/id/10149) G. O'Brien is referred to as "George 'Darby' O'Brien" in the article. I'm trying to decide if that is really George Darby (darbyge01) or Darby O'Brien (o'brida01). It looks more like the former than the latter.
Other major leaguers are Bill Nelson and Ed Eiteljorge. I'm not sure if J. Cantillion is manager Joe Cantillion or not - I'm guessing not.