Brentford will be missing Maxime Colin for Saturday's trip to Rotherham United due to an abdominal injury.
The Frenchman missed the 3-0 win over Wolves as the long-standing injury finally got the better of him and he is unavailable for the game at the New York Stadium.
He said: “Maxime Colin is out. We're not sure for how long. He's been seeing a consultant and we're waiting to find the results of that in the abdominal area.
“It's a strain in the groin area. It's what caused him to miss Tuesday's game with Wolves.”
Lewis Macleod, who made his long-awaited debut against Brighton earlier this month, has been out of action with a knee injury and the Scot is expected to be out for two weeks.
Smith added: “Lewis Macleod has still not trained yet. I think he'll be another couple of weeks before he is back training. It's a knee injury. He's slightly tweaked his medial ligament I think.”
Alan McCormack will also miss the trip to Rotherham but could return for the following weekend's visit of Charlton.
Smith explained: “Alan McCormack has trained today. It was nice to get him back on the training round and he'll train all week next week. He's not travelling with the squad. It's been a long time since the Walsall game.”
There is better news regarding Scott Hogan who will return to action for the development squad on Monday.
Smith confirmed: “Scott Hogan will play a part in the game against Crystal Palace on Monday which will be good to get him out on the pitch at Griffin Park.”
The Bees head coach may be making changes from the side that beat Wolves 3-0 in order to keep the legs as fresh as possible.
He said: “I've always been wary of players playing three games in a week. It can take a lot out of the legs and we're quite a young squad.”