[prewinter]

O'Brien played 6 games for the Terriers in July 1913, and I found a reference that he played for the Alpen Braus in 1913 (a semi-pro club in St. Louis), and subsequently that his first name was Ray (St. Louis Star and Times, July 13, 1913). So I went to Baseball-Reference, put in Ray O'Brien, and found Raymond J. O'Brien (obrien001ray), from St. Louis, who played a ton of seasons in the minors (starting in 1913), and a handful of games with Pittsburgh in 1916. So here are the photos. First, Ray J. O'Brien, pictured with Davenport in 1914 (from the Davenport Daily Times, April 22, 1914). The O'Brien from the 1913 Alpen Braus.

Do they look like a match?

Followup: The Decatur Herald and Review reported on July 6, 1916 that "O'Brien, the St. Louis youth taken on by the Pirates from Davenport... once played first base of the St. Louis Feds." Not absolute proof, but more evidence.