2019 (Orlando City SC): Started eight of his 11 appearances and recorded 838 minutes and three shots in his second season with Orlando City SC.
2018 (Orlando City SC): In his first season with Orlando City, O’Neill started all 13 of his appearances and played 1,118 minutes. He recorded six shots, including one on goal.
2017-2018 (SBV Excelsior): Transferred to SBV Excelsior for the 2017-2018 campaign, making one league and one cup appearance.
2016-2017 (NAC Breda): O’Neill was loaned to NAC Breda of the Dutch second division, where he made 25 league appearances, including one goal.
2015-2016 (Royal Excel Mouscron / Cambridge United): O’Neill was purchased by Cypriot club Apollon Limassol and in August of 2015 and subsequently went out on loan to Royal Excel Mouscron of Belgium and Cambridge United of England.
2015 (Colorado Rapids): O’Neill recorded 286 minutes while starting three of his four appearances in his final season with Colorado.
2014 (Colorado Rapids): O’Neill started all 21 of his appearances in 2014, recording 1,890 minutes. He scored his first MLS goal on May 24 in a 4-1 win vs. Montreal. The defender totaled six shots, including four on goal.
2013 (Colorado Rapids): Recorded career highs in appearances (26), starts (24), minutes (2,196) and shots (8) in his second season in Colorado. O’Neill started and played the full 90 minutes in Colorado’s lone playoff game of 2013, a 2-0 loss at Seattle.
2012 (Colorado Rapids): Played four minutes in one contest during his rookie season. He was signed by Colorado as a Homegrown Player on June 19. O’Neill made his professional debut against Portland on September 5.
O’Neill was called up to the United States senior squad in January 2015, and featured for the U.S. at the 2013 FIFA U-20 World Cup. He made his debut for the U-20 U.S. National Team on October 10, 2012.
Signed by Sounders FC as a free agent on January 14, 2020.