O'Neill (Mariners' No. 2, No. 64 overall) had 24 homers in the regular season, and with two on and two out, he hit his first home run of the postseason -- a three-run walk-off shot out to left field.
"I was just really fired up going to the plate," O'Neill told MiLB.com. "Extra innings, postseason, little bit of a competitive attitude running through my veins. I just wanted to get up there and get Ian [Miller] in from second base and get the ballgame over with.
"I knew it off the bat. I saw a good seven sliders that at-bat, so I had a pretty good idea of how it was breaking. I put the barrel on the ball and good things happened."
Moore, the Mariners' No. 10 prospect, carried a perfect game into the seventh inning, but a bunt single from Kean Wong disrupted Moore's bid for history.
Wong was caught stealing during the following at-bat and Moore kept on cruising. The 22-year-old right-hander threw 71 of his 101 pitches for strikes, giving up just the one hit as he faced the minimum through nine.
The 101 pitches were a season high for Moore, who showed no signs of slowing down as he struck out the side in the ninth and finished with eight strikeouts.
• Box score
Moore went 9-3 with a 3.16 ERA in 19 starts for Jackson this season, including one complete game, but he was stuck with a no-decision Wednesday.
Hu fired eight scoreless frames in his final start of the regular season and picked up right where he left off, giving up five hits in 7 2/3 scoreless innings to begin the playoffs.
William Boor is a reporter for MLB.com. Follow him on Twitter at @wboor. This story was not subject to the approval of Major League Baseball or its clubs.