Barnsley striker Mido could be sidelined for up to three months due to injury and fellow new signing Toni Silva will also miss the start of the season.
Mido joined Barnsley earlier in the summer, but damaged his hamstring prior to the recent pre-season friendly against Doncaster Rovers.
He is now facing a lengthy spell out of action, with forward Silva and goalkeeper Luke Steele also likely to sit out the Capital One Cup tie against Barnsley manager Keith Hill's former club Rochdale on Saturday.
"It's a massive blow, but there's nothing we could have done to prevent them," Hill told the Sheffield Star.
"Mido pulled his hamstring shooting in the warm-up against Doncaster and the scan's revealed it's a bad injury, it's very serious.
"It's a shame both players are injured, but we've just got to get on with it."
Hill confirmed he will now be trying to sign a striker before the trip to Rochdale to compensate for the injuries to Mido and Silva.
He added: "We've got an obvious problem, we need to get a striker in the building as soon as possible. We're going to have to dip into the transfer market.
"It's going to be difficult to get a recognised striker with less than a week to go until we play Rochdale, but we'll be trying our best."