Craig Gardner hit a first-half winner, while Young was outstanding over the 90 minutes and O'Neill said: "We played some great stuff in the first half and Ashley was mesmeric. He was a great outlet for us and caused havoc.
"There were moments in the game when he was unplayable. The confidence he has got comes from having great ability.
"Agbonlahor was also terrific for us and he is getting stronger and better by the game.
"We should have capitalised more in the first half and then West Ham came at us after the break and had the bulk of possession.
"I think our exertions at Tottenham earlier in the week (where they were held to a 4-4 draw) may have taken their toll and when we freshened things up we started to get a grip again."