Key man O’Connell has undergone two operations on his damaged knee, but has not pulled on a Blades shirt since September 2020.
Without the former Brentford man’s qualities, both defensively and in attack, United have struggled badly and were relegated last season from the Premier League.
O’Connell has been working at United’s Shirecliffe base, and is sometimes granted leaves of absence to continue his rehabilitation elsewhere.
Heckingbottom was asked about the 28-year-old at his pre-match press conference this afternoon, ahead of tomorrow’s clash against Queens Park Rangers.
“It's pointless putting a timescale on it,” the Blades boss said.
“We’re just working with him and giving him the support he needs. He’s in the building around the boys with a smile on his face but it’s a tough place to be.
“I’ve been there, and Jack’s in that position. It’d be foolish for us to put a time on it.
“He’ll get all the support he can and it’s good to have him in and working hard, which is an important thing for his own mental state. But we won’t put anything on Jack. I had him back training with me [in Heckingbottom’s caretaker stint] but it’s just been those final hurdles, and getting over them.”
Asked if O’Connell was kicking a ball yet, Heckingbottom added: “He's back in the gym doing strength work for his knee.
“We’ll just continue down that route. He works hard doing all he can do, so there’s no rush and no pressure.