Ireland 67 for 2 (O'Brien 32, Ajekun 1-10) beat Nigeria 66 for 9 (Adedeji 19*, Young 4-13, Adair 2-10)
Craig Young's 4 for 13, his T20I career-best returns, and Mark Adair's 2 for 10 locked up Ireland's place in the playoffs of the men's T20 World Cup qualifiers as Nigeria were restricted to 66 for 9 before the target was knocked off with 13.5 overs to spare for an eight-wicket win in Abu Dhabi.
Ireland, who pulled off their quickest T20 chase on the day, might even top Group B, but need Jersey to upset Oman on Sunday to produce a tie at 4-2 at the top of the table, with the automatic berth for the group winner at the T20 World Cup decided on net run-rate.
Gareth Delany and Adair made the early inroads for Ireland after Nigeria decided to bat first at Sheikh Zayed Stadium. A googly from Delany bowled Daniel Akejun in the second over before a run out off Delany's bowling got Ireland their second, Sulaimon Runsewe sent packing by George Dockrell. Adair claimed Daniel Gim in the fifth prodding away from his body for an edge behind to make it 13 for 3.
Nigeria crawled to 33 for 4 by the halfway stage before Young made his first strike, bowling Chimezie Onwuzulike after he was late into a drive. His second came in the 17th when Isaac Okpe was fooled by a slower ball to be the bowled. Two more fell in the 19th when Sylvester Okpe became the third batsman to have his stumps knocked back by Young and Vincent Adewoye skied a slog to cover where Dockrell took a catch.
With Ireland keen to lift their net run-rate above Oman to keep the door open to finish atop the group, Paul Stirling and Kevin O'Brien attacked throughout the Powerplay.
Stirling made 11 before he edged behind driving hard at Okpe in the third over but O'Brien kept clearing the infield for six boundaries in his 32 off 17 balls before he fell in the sixth, bowled by Akejun backing away to drive over cover. Delany and Adair teamed to knock off the final 13 runs with the winning runs coming via three leg-byes.
Nigeria have a final chance at a consolation win over Hong Kong on Sunday.
Peter Della Penna is ESPNcricinfo's USA correspondent @PeterDellaPenna