Sunderland's first opponents of the Championship campaign have been dealt a major blow after Derby County striker Darren Bent was ruled out until Christmas.
The Black Cats host the Rams at the Stadium of Light on Friday, August 4 but Bent will be missing after he picked up a knee injury in their recent win over Port Vale.
Derby manager Gary Rowett said: "He went to see a specialist in London after the injury at Port Vale and it's not good news.
"He's probably going to be out up until around Christmas time so it's a little bit of a blow because he's looked sharp in the games so far but it's something we're going to have to deal with."
With Bent missing, Derby started their friendly against Kaiserslautern at the weekend with Chris Martin up front in a 4-3-3 formation with support from Andreas Weimann and Johnny Russell.
Rowett, though, was giving little away in terms of his formation and team selection ahead of the opening game of the new season away at Sunderland.
"I wouldn't say that the team [against Kaiserslautern] is completely geared towards Sunderland but we wanted to look at one or two things," he added.
"That is in terms of both the formation and also personnel too, just to see how that looks together. I have told the players this, nothing is definitive at this stage.
"We have plenty of games to iron out the exact starting line-up."