In 2270, Orion pirates boarded the Huron and injured him and two other officers, rendering them unconscious. They were discovered by a landing party from the USS Enterprise. Dr. McCoy performed minor surgery on O'Shea and he later made a full recovery. (TAS: "The Pirates of Orion")
Background information Edit
O'Shea's was one of the character voices provided by James Doohan. He is described in the script as "a craggy-faced man".
O'Shea wore no rank insignia, therefore making it unclear whether he was a captain by rank, or by position only.
Star Trek Log 5 gives his first name as Svenquist.