Sheffield United defender Jack O'Connell has suffered a setback in his recovery from a serious knee injury.

The 26-year-old underwent surgery at the end of September after the decision was taken that a long-standing complaint, that has hampered him throughout his senior career, needed rectifying with an operation.

It was hoped he would be able to return to action sometime next month, with Blades boss Chris Wilder recently stating that O'Connell would be included in his 25-man Premier League squad set to be submitted when the transfer window closes.

It remains to be seen if that will be the case, after Wilder provided an update on the central defender ahead of Saturday's FA Cup fourth-round tie against Plymouth.

"Jack has suffered a little bit of a setback. We knew that would happen, because his situation isn't straightforward. We know we have to be really careful with him," said Wilder.

"We have to manage his load, as it were, and it was always a difficult assessment to make (about when he will return to action).

"It's a setback for us and, more importantly, it's a setback for the boy. He'll come through it. It was never, like I say, going to be straightforward."

The cup tie against Plymouth provides the Blades with some respite from what has been a disappointing Premier League campaign.

The previous round saw Wilder's team finally get a first victory of the season, before going on to defeat Newcastle three days later to end their winless league run.

Wilder hopes for a repeat scenario, with daunting fixtures forthcoming next week against Manchester United and Manchester City.

"We did it going into the Bristol Rovers game, and after it into the Newcastle game," said the Blades boss.

"There were even positive signs in the Tottenham game, despite the defeat. There's still belief in the players. We keep going.

"We'll dust ourselves down, as we've done this week, and see if we can get a result and through to the next round.

"I see no downside to winning a game of football, whether it is an eight v eight out there on the training pitch, a pre-season friendly at Stocksbridge, an FA Cup tie or a Premier League game.

"And we've done exactly the same process, coverage and attention to detail regarding Plymouth as against Spurs. I think that's only right as well. I've got a huge amount of respect for (Plymouth manager) Ryan (Lowe) and his team."

Oli McBurnie (shoulder), Lys Mousset, Jack Robinson and Ben Osborn will remain unavailable due to injuries, but Jack Rodwell is set to return to the squad.