The Ulsterman, who revealed the club had had a bid for Bolton striker Kevin Davies rejected on Monday, has not given up on that proposed deal and is also considering dipping into the loan market after sending Wes Brown and David Vaughan for scans on injuries picked up during yesterday's 1-1 FA Cup fourth round draw with Middlesbrough.
Skipper Lee Cattermole, who missed the clash with his former club because of a hamstring problem, joined the pair as O'Neill prepared for a busy final day or so of the January window.
He said: "I am a bit concerned because we have a few problems to overcome.
"We have a couple of injury problems, just when you thought there was light at the end of the tunnel, that we were getting a few people back.
"Then suddenly, you play a game, you lose a couple of players and you are less than 36, 37 hours away from transfer deadline.
"As I have often said here, which has always been my concern, on February 1, that's it, so we might have to look at some sort of loans."
The recruitment of a striker was already a possibility with Nicklas Bendtner sidelined until at least the middle of next month with a fractured nose, and Davies has been in the Black Cats' sights for several days despite Bolton boss Owen Coyle's hopes of hanging on to the 34-year-old.
O'Neill said: "We have made an offer for Kevin Davies, but that has been rejected at the moment.
"We will try to see if there is something we can do, but I just wouldn't mind getting one or two players in if it's at all possible just to alleviate the problems we are obviously going to face in the next couple of months."
However, the injuries to Brown and Vaughan have increased the scope of Sunderland's need.
O'Neill admitted: "We are looking at a number of aspects - it would be ridiculous if we weren't looking at them.
"It does present us with a problem with the games and we still need some points on the board."
O'Neill's fresh selection problems have ended any prospect of homesick midfielder Craig Gardner being allowed to return to the Midlands, with former club Birmingham among his suitors.
The manager said: "No, no, no. We have got enough problems here trying to get a few players in at this minute to help alleviate the situation.
"No, Craig won't be going anywhere now, and in fairness to the lad, he hasn't been making any big showing.
"He knows there has been interest - we have kept him up to date with interest from down in the Midlands and maybe at some stage, we will think about that.
"But now, we really need him and he is doing fine for us."
Amid the ongoing flurry of activity, O'Neill can at least console himself with Fraizer Campbell's return to fitness and form.
The 24-year-old came off the bench as a half-time replacement for Connor Wickham on Sunday and announced himself in style with a 59th-minute equaliser to deny the Championship side a famous victory at the Stadium of Light.
Campbell has spent the last 17 months fighting his way back from two cruciate ligament injuries in the same knee, and his delight at being able to play again and contribute was unbounded.
He said: "It was brilliant. I have been out for a long time, as everyone knows, and it was quite emotional out there to actually get on the pitch and score.
"It's been such a long time and to get back out there and to be on the pitch, let alone score, was brilliant."
