Dean Smith has a selection headache at right back with Josh Clarke ruled out of Brentford's trip to Norwich.
Henrik Dalsgaard, who also plays in that position, has just returned to fitness and Smith is unsure whether it's worth a risk starting him.
That leaves Nico Yennaris, whose best position is in the midfield, as the other option to play at full back.
There is better news going forward as Lasse Vibe has returned to full fitness, while Alan Judge suffered a minor setback in his recovery from a broken leg.
Smith said: “We've got a few little niggles. Josh Clarke went over on his ankle. He's going to miss Norwich but we hope he can be fit for Aston Villa.
“Ollie Watkins had a slight scare with his ankle but he's fine and he'll be ready for Friday. Henrik Dalsgaard has trained with us all week and while he may not be ready to start, he's certainly in our thoughts.
“Lasse Vibe is back to full fitness. Lewis Macleod is itching to start. Alan Judge is with us all week but unfortunately he had a little niggle which meant he couldn't play in the Manchester City game.”