O'Neill revealed he had turned down a series of offers for the player to go out on loan.
He said: "David has had a really tough time with injury. Of course, I have only known him as he is making his way back from it.
"He might have seen how Fraizer Campbell has fought back from the injuries, but I am delighted for David.
"He is an exceptional lad, he is, honestly. You would be very happy with him around about the place."