Aston Villa manager Paul Lambert says it is unclear how long he will be without striker Darren Bent, who has suffered an ankle injury.
Lambert will again be without the services of Villa's record signing when Manchester United visit Villa Park on Saturday.
Bent suffered the injury in training last week, forcing him out of the 1-0 victory at Sunderland and the striker has since undergone scans to determine the extent of the damage. He missed the last three months of last season with an injury to the same ankle.
"Darren had a scan on Wednesday, and it's still too early so we will have to go with the same squad of players," Lambert said.
"He's doing okay at the minute, but we'll have to wait and see. It is the ankle he injured against Wigan [last season], so we will wait and see. It is not right at the moment."
Lambert has called on his players to be brave enough to rise to the challenge of taking on the Premier League leaders.
"Manchester United are a top side, but you don't want to be buried in your own half for 90 minutes. You have to try to do something in the game," he said.
"I think every game is really tough, but when Man United come it is a special game. Everyone wants to beat them because they are the top of the tree. It is a great occasion for us.
"You need a bit of luck, too. We have to believe that we can win. The belief in the football team at the minute is there. The stadium will be vibrant. There will be a massive crowd, and it will be up to us to try and give them a problem.
"But if you go gung-ho against Manchester United, they will pick you off. That's me being realistic, but you got to give it a go as well. We're at home, and will do everything we can to try and win."