DARIUS Henderson and James Henry will undergo scans on Thursday to determine the extent of hamstring injuries sustained against Watford.
The duo were forced off during the second-half of the Lions' goalless draw at Vicarage Road after pulling up within minutes of each other and Kenny Jackett confirmed that both players are major doubts to face Derby County on Saturday.
One report has since suggested that Henderson could be out for up to three weeks but Henry's strain is less severe, with Jackett describing the problem as "neural".
Jackett said: "If they're not fit for Saturday, we have players that can come in in that situation. Andy Keogh came on for Darius against Watford and there's a number of people who can fill in on the right.
"The squad has to be good enough to be competitive and it's an opportunity for somebody else."