There are also question marks over Daryl Murphy and James McCarthy for Friday night's crucial World Cup 2018 qualifier, while opponents Wales have fewer problems to contend with - in-form forward Tom Lawrence being their only major absentee - following the recent return to action of star man Gareth Bale.
Asked about his side's injury problems, O'Neill told reporters: "How long have you got? It's the lengthiest list of injuries that I have known since I have come into the job, and unfortunately it's happened at a really crucial time for us.
"However, other players will have to step up and just be ready for Friday. Do you know, I have often said this before, that you just curse your luck and get on with it.
"The irony of all of this here is that way back when Gareth Bale got injured in November-time, everybody was talking about Wales possibly having one of their major players out of the team, and it turns out that we are the ones who are doing the suffering. But it is what it is and we'll get on with it and we'll be ready to go on Friday."
Ireland have a four-point advantage on Wales in Group D as the midway point in qualifying for Russia 2018 approaches.