Bristol City face six weeks without their defensive linchpin Tomas Kalas.
The Robins' record signing was stretchered off with a suspected hamstring tear after half an hour of City's 3-1 win at Hull City.
Speaking ahead of the visit of Middlesbrough on Saturday, head coach Lee Johnson revealed a scan had confirmed their fears.
He said: "Tomas had a scan yesterday, it is a grade two [tear] of the hamstring. He's a strong lad but it's probably going to be somewhere between four and six weeks.
"It feels like we've got some key players out with Bailey and Korey and Kalas particularly in that centre-half area of the pitch, but we're alright.
"With Kalas’ hamstring, everything will be looked at: training, has he been driving a lot, his sleeping - everything so it can be avoided."
Meanwhile , although he has been called up for Hungary's upcoming European Championship qualifiers.
Johnson hopes to have him fit and available for the trip to Stoke on Saturday, September 14.
Bristol City take on Boro in the early kick-off on Saturday at 12.30pm.
