O'Brien was a second baseman for the Crusader baseball team under the legendary Jack Barry. He earned the starting spot as a sophomore, when the team posted a 10-6 record. During his junior year, the Crusaders lost their opening game and then won their remaining 15, being declared Eastern Champions (there was no college World Series at this time). O'Brien batted .352 as a junior, and then .342 as a senior when he scored 19 runs in 18 games. The Crusaders posted a 14-3-1 mark that year. O'Brien also played three years of football at HC, with his biggest game coming when he threw two touchdown passes against Temple, coached by the legendary Pop Warner. The Detroit Tigers pursued O'Brien for a pro career, but World War II called and he served his country gallantly, being awarded the Navy Cross posthumously as he was killed in action on July 22, 1944.