Cristian Romero had to come off early in their 4-3 loss to Chelsea, while Brennan Johnson was also substituted.
Micky van de Ven was another who was unable to play the full 90 after returning to the starting lineup.
Post-game, the Australian said: “Romero is just obviously hugely disappointing. He felt something in his quad. He trained really well.
"He wasn't the one I was worried about, to be honest, but, you know, it's just like I said, the way the season's going for us unfortunately. So we just have to wait and see.
“Brennan just didn't feel well. He didn't feel well at half-time, but he wanted to give it a go, but he just wasn't feeling 100% so I had to take him off.
“And then, well, the plan was always for Micky to play 60/70 (minutes) today.
"Obviously, I thought Romero would be okay to play 90, but Micky, probably 60/70. So we were always going to take him off.
"He didn't feel anything significant. He just felt tightness, but we were always going to take him off anyway.”