Now, the side face the prospect of taking on the group favourites without their best player.
Bradley, who has also been booked three times in five Premier League appearances this term, was shown his second yellow card of the qualifying campaign in the 76th minute for a tackle on Lukas Haraslin.
O’Neill described the decision as “extremely disappointing” and felt his player had tried to pull out of the challenge.
“There were worse tackles in the game and one just before that was particularly poor on Isaac Price that the referee let go,” he said. “To produce a yellow card for that was disappointing.”
Speaking on BBC Sport NI, former Northern Ireland and Leeds United defender Stuart Dallas said Bradley had given “the referee a decision to make” but agreed with his old international boss that the decision ultimately was harsh.
If not for the resulting suspension, it would have been a mere footnote in an otherwise excellent performance.
Bradley was one of four players in the starting XI who went into the game knowing a booking would rule them out of Monday’s game, but Hume said they do not wish to curb his aggressive edge.
“We spoke before the game about the boys who were on yellows trying not to get one, but it’s one of those things,” he explained.
“You can’t go into a game trying not to get booked. You’ve got to play to your strengths.
“He’s full throttle. He’s 100% all the time.”
Since making his full Premier League debut in January 2024, Bradley has started 15 of his country’s 17 games, missing only the friendlies against Sweden and Switzerland in March.
Quite how to compensate for his loss gives O’Neill yet another thing to consider as he plots how to pull off what would be the biggest result of his second spell in charge.
While there is no like-for-like replacement in the squad, Oxford United’s Brodie Spencer figures to fill the void at right wing-back against the four-time World Cup winners.
“You’ve seen Brodie play left wing-back, right wing-back, he’s even played in a back three. We know how strong and athletic he is,” added Hume.
“Obviously Conor is going to be a big miss, but we’re a big group, we’re a strong team and we’re all together.
“It’s something we have to deal with and we’ll be ready.”
