The former Villa boss hailed the 22-year-old after he celebrated signing a new three-year contract by scoring what proved to be the decisive goal of the contest having played a key role in Nicklas Bendtner and Stephane Sessegnon’s strikes.
“I am very pleased with the performance and some of the goals we scored were excellent,” O’Neill told reporters.
“I thought James was magnificent for us. He was a constant threat to them throughout the afternoon and if anything he is just getting more confident about his game.
“I just thought he was really excellent. He made the first goal, although Nicklas Bendtner still had plenty to do when it came into the box; he helped make the third goal and obviously contributed a goal himself.
"Overall he was brilliant. He has great enthusiasm and great determination and thirdly he has got some ability and he is trying to improve. He is loving it.
"He stepped in to play and he said somewhere that, amazingly, he is not in awe of the whole thing. He didn’t mean to be disrespectful to anyone at all but I just think that has probably helped him.”
O’Neill went on to reveal that John O’Shea would miss Tuesday’s FA Cup quarter-final replay against Everton with an unspecified injury but is certain his team will go into the contest with confidence high.
“I am delighted with the win keeps the momentum going," he added.
"We are on 40 points on the board and if you had given me that in December I would have taken your arms off for it before the end of the season never mind anything else.
“There were some brilliant performances in the second half – however, the moment we took our eye of the ball they scored a brilliant goal when Taye Taiwo scored a free-kick.
“We’ve picked up six points from our last three games, which is terrific - it works out at two points per game. I’m delighted with the team, it was a great response from the defeat at Blackburn and it sets us up well for Tuesday night.”