The midfielder will remain at Bramall Lane until February 24 - the day before his 21st birthday - as per the terms of his youth loan.
Blades boss Nigel Clough said: "We have extended the loan of Conor and will see how things progress. Obviously the lad wants to be playing regularly, so we thought in the first instance it would be wise to sort out the short-term.
"He has started a lot of games since he arrived, he does a lot of good things, but as you would expect from a young player, has areas of his games to work on.
"Conor is such a bright lad, though; he has a real willingness to learn and improve and always has a smile on his face.
"He will certainly have benefited from this loan and he has proved to be a useful performer to have in our squad too."