Thomas Tuchel confirmed Tammy Abraham sustained a recurrence of an injury which has kept him out of action in recent weeks, urging the Chelsea forward to be cautious with his recovery.
Abraham has not featured for Chelsea since February 22, due to a combination of injury and his form in training.
Coming into the FA Cup quarter-finals, no player had scored more goals in the competition this season than Abraham, who had netted four times across the third, fourth and fifth rounds.
However, the 23-year-old was again absent from the squad at Stamford Bridge on Sunday, and Tuchel – who on Friday instructed Abraham to be patient as he waited for an opportunity – revealed Chelsea's number nine had suffered an injury.
"Yes, he quit training yesterday after a five-minute warm-up so there was more or less no chance he could join the squad," Tuchel told a news conference after Chelsea's 2-0 win over the Blades.
"It was the same injury, more or less, but he had a re-injury in more or less the same spot where the first injury was so he is in pain and he had to quit the session after five minutes with no chance he could join us today.
"The most important thing for Tammy is be fit. The second is then to take things step by step, to train and fight for his way back.
"His way back is maybe to be a substitute and to be hungry and full of quality in training. These are the next steps.
"Now is not the time to worry about the first eleven because he is out now for many games, unfortunately too many games.
"It's absolutely not his fault and he is hungry to come back. He tries all the time but this is the risk with pushing the players to be back as soon as possible.
"It was an accident in training. So nobody's fault. So now is a kind of restart and we hope he can use the next two weeks to get fit again."
Despite his recent struggles, Abraham is Chelsea's leading scorer this season with 12 goals in 30 matches across all competitions.
He has taken 10 of 16 'big chances' – opportunities from which Opta would expect a player to score – far better than Timo Werner's rate of eight from 26.
Of Chelsea's three central strikers, Olivier Giroud (103) boasts a better minutes per goal ratio than Abraham (127), while Werner is down at 284.
Creatively, Werner has been far more profitable, crafting 31 opportunities, in contrast to 13 from Abraham.