Manchester United manager Louis van Gaal has suggested that Robin van Persie will not be ready to start against Chelsea on Saturday.
Van Persie, 31, has missed United's last seven games with an ankle problem, but there could be an opening in attack at Stamford Bridge as Van Gaal is considering using Wayne Rooney as a holding midfielder due to injuries to other players in his squad.
However, although Van Persie has been back in training for more than a week, Van Gaal is reluctant to rush returning players into his side and feels the striker is not in the right condition to feature.
"No. He has to play matches," Van Gaal said in a news conference. "When you are injured you don't use your muscles. Then you have to use your muscles, but you have to use them in another way than playing football.
"Then he has to play matches and exercise with the ball -- that's the difference. Then you have to build up in games, in minutes, in training sessions -- all those kinds of things."
United will be without the injured quartet of Michael Carrick, Daley Blind, Marcos Rojo and Phil Jones on Saturday, as well as the suspended Jonny Evans.
Luke Shaw, who has not featured since last month's FA Cup defeat to Arsenal, is set to replace Blind. Van Gaal then faces a choice between Paddy McNair, whose last start was at Swansea in February, and Tyler Blackett, who has not begun a game since January's FA Cup tie at Yeovil, in the centre of defence.
And he admits he is worried about their lack of match sharpness, adding: "Yes, but that's also a truth like a cow. That's a Dutch expression -- it means a rhetorical question. You know the answer already."
Van Gaal said vice-captain Carrick could be out for two weeks and clarified the other injuries by explaining: "Blind is foot or ankle. Rojo is adductor. Jones is also a foot or ankle."
United face one of the division's taller teams in Chelsea, who often field seven players who are six foot or more.
"When you see our selection, our height is not tall enough," Van Gaal said. "We have a big deficit in height. When you speak with a basketball coach, for example, one or two centimetres is very important.
"In football, it is the same because when you see the statistic, a third or fourth of all the goals the team is scoring are from set-plays. Then the height is very important."
United had a poor record against top-seven sides under former boss David Moyes last season but have an excellent one under Van Gaal.
"It is because we have now the theory of games we have to play against the better teams," Van Gaal said. "But when the better teams came in the early stage of our process, then we would have lost."