Bailey, who injured his thigh muscle scoring in the 3-0 win over Everton last weekend, will be out until after the October international break. Sanson will be out for a month with a hamstring strain suffered in the Carabao Cup penalties defeat at Chelsea in midweek.
However, John McGinn is available for the trip to Manchester United after suffering slight concussion in the win against Everton.
Smith said: “Leon has a strain which is likely to keep him out until after the international break. We would be hopeful that he would be available for the Wolves game but we will need to assess him nearer the time and see how he progresses over the next ten days or so.”
And on Sanson, he added: “He just felt a twinge in his hamstring. We don’t believe it’s going to be a bad one.”
Meanwhile, Villa starlet Cameron Archer has praised the faith boss Smith has put in him.
The 19-year-old burst onto the scene last month when he netted an impressive hat-trick in the 6-0 thrashing of League Two side Barrow in the Carabao Cup.
He also netted against League One Wycombe in the EFL Trophy, playing for Villa’s under-21s.
On Wednesday he was handed another chance in the Carabao Cup with the first team, starting and equalising away at Chelsea.
He said: “It’s given me opportunities and I took them today and against Barrow. Hopefully I can keep getting opportunities.
“It was a great experience in front of 38,000 and it was a crazy feeling scoring. I don’t score many headers. I was delighted when I made contact with it and it went into the back of the net. It’s amazing when you have that faith from the gaffer. It boosts your confidence even more.”