Shane Long will lead the line for Ireland tonight against Slovakia with their forward options having been decimated by injury.
Jonathan Walters (hamstring), Daryl Murphy (calf) and Kevin Doyle (shin) have all returned to their clubs, while veteran striker Robbie Keane is sidelined by a knee problem.
Of the quartet, former Tottenham Hotspur hit-man Keane’s injury appears the most serious.
But O’Neill has hinted that the 35-year-old could still travel with the squad to France this summer, even if he is not fit enough to make the final 23-man party to contest the European Championships.
“Robbie would be thinking he would want to try to make the 23 first and foremost, and then we will see how things develop after that,” said O’Neill of his record goalscorer.
“But he has been very influential in the group, he’s been very supportive the whole time he has been here and even when he hasn’t started in matches, he’s still with the team, so that is a thought, I must admit.”
Ireland come into the contest having beaten Switzerland 1-0 on Friday, defender Ciaran Clark’s second-minute effort the difference between the two sides.
But O’Neill admits it would be heartening to see his team a little more potent in front of goal.
“I’d like to score a few more goals if we can and I’d like us to try be a bit more confident in possession,” he added.
“While we want to win these games it’s a bit of a trial at the same time.”