Bodymoor Heath was being lashed with rain, and The Belfry across the road must have doubled in water hazards, but it would take more than a Midlands monsoon to extinguish the fire of James Milner, that all-action embodiment of Villa's youthful energy.
Under the canny tuition of O'Neill and John Robertson, Milner has matured, moving inside and delivering eye-of-the-needle passes to split defences.
"He played a ball for a goal in training which you wouldn't believe,'' said O'Neill, shaking his head almost in amazement at Milner's vision in picking out Marc Albrighton.
"James' confidence is absolutely sky-high. The ball he played to Richard Dunne against Hull showed that (in the 3-0 home win on Dec 5). The ball dropped out from a corner and James picked it up in midfield. The obvious thing was to put it straight back into the box because Hull were advancing out. But James spotted Dunne.''
Rather than hoist the ball over Hull's back-line, Milner jabbed it low at an angle for Dunne to run on to.
"It was an amazing ball. Dunne took a stride and put it in the net.
"James is getting into little areas outside the box, which is now part of our game that probably wasn't there a season ago. Stiliyan Petrov has been able to give him the ball.'' Which Milner uses to devastating effect.
"I am absolutely thrilled with him.'' Milner's development is good news for England as well as Villa.
Fabio Capello has been impressed by Milner's displays for England out wide, notably against Brazil in Qatar. O'Neill believes that Milner can force his way into the middle, shining for his country in the centre as he does for his club.
"James could play in the middle for England, absolutely, even though England are very, very strong there.
"Frank Lampard and Steven Gerrard are really gifted players but James could play in there. James has gone into midfield [for Villa] and played as if he owned the place.'' The Holte End would doubtless dissolve with laughter if Milner replaced their former captain, Gareth Barry, in England's midfield.
Capello's No 2, Franco Baldini, will watch Milner (and fringe candidates like Stewart Downing and Ashley Young) against Fulham on Jan 30.
Milner is sure to be in Capello's 23 for South Africa, enjoying the counter-attacking style expected to define a rare World Cup in cool climes.
"James will relish that,'' continued O'Neill. "He's played it often enough with us here. He's grown greatly in confidence with the ball since he arrived here. He now feels he won't be worried about miscontrolling the ball when he's with England, about not leaving a mark on the England scene. I couldn't see him being fazed.''
Milner is not alone in varying and strengthening his game under O'Neill.
Downing, who made his name as a left-winger with Middlesbrough, has featured in the centre for Villa, even pinging some fine passes with his right foot.
"The last game Stewart played for Boro, James was right-back and Stewart gave him a tough old time.
"But I always felt Downing was not just a left-winger, that he could drift like Ash and James and take it on to his right side. Stewart's a fine footballer and has not surprised me with his skill. I saw Stewart play for Middlesbrough off the centre-forward and look comfortable.
"I saw James play for Newcastle off the centre-forward and look comfortable. Ash has played off the centre-forward for us not a problem.'' Mainly used to stretch opponents, Young prospers under O'Neill but has yet to show his class for Capello.
"I'm surprised people are asking me about Ash,'' added O'Neill. "Maybe it's because James is getting a lot of limelight. If it's the case that Ash hasn't settled in with England '' Villa's manager paused.
"When he feels comfortable in an environment, he is really outgoing. It didn't take him long to settle in here! Ash has been brilliant this season. Brilliant.
"We have a group of young talented players so we know we will be fine when we have the ball. But will we be OK when we don't have the ball?
That's the only worry. You wouldn't call them the most physical of players.'' Yet they have a huge work-rate, particularly Milner, a quality witnessed in Wednesday's extraordinary 6-4 victory over Blackburn Rovers that carried Villa to Wembley.
"You only have to look at Ash coming back to cover for the full-backs,'' enthused O'Neill, "and Stewart getting back into position to pick things up.''
Always thoughtful on footballing trends, Villa's manager argued that players can never ease up because supporters will be on to them. "Fans are becoming more impatient. Away teams feel that if they can hang in there, the home crowds will get more anxious and this anxiety can transmit to the players.
"In my playing days, crowds still got anxious but fans do demand more of the player now. His [improved] money situation hasn't improved his ability but the fan thinks: 'I'm paying big money to watch this game, I'm expecting you never to miscontrol this ball.' "There is a greater alienation than ever between fan and player.
I'm delighted that players have more power than ever but it has gone too far: players cannot take the money and not take the responsibility with it.
Players have to learn to live with this impatience.'' So when Rovers took a two-goal lead, Villa fans could have become jittery and critical but O'Neill's players kept their nerve.
"We could have capitulated. If you'd told me Blackburn were going to score four here, I wouldn't have turned up!'' O'Neill laughed at what the scout for Satruday's FA Cup foe, Brighton & Hove Albion, must have made of Wednesday.
"I am quite sure his report will start 'you are never going to believe this'!''
Everyone will believe that Milner shone, and Brighton will certainly be relieved if Milner is given a well-earned rest. Under O'Neill and Capello, Milner has bigger missions in 2010.