FC Schalke 04 captain Benedikt Höwedes faces up to three months out with a hamstring injury.
Preview: FC Schalke 04 - SV Werder Bremen
It was initially hoped that the FIFA World Cup winner, who limped off 20 minutes into the Royal Blues' 2-0 victory over the Fort Lauderdale Strikers in the Florida Cup 2016, would be out for around a month, but further tests have revealed the problem to be worse than first thought.
As well as missing the Bundesliga restart, the 27-year-old defender will also have to watch Schalke's UEFA Europa League last 32 double-header with Ukraine's FC Shakhtar Donetsk from the sidelines.
The Royal Blues, currently two points outside the top four in sixth, return to competitive action against SV Werder Bremen this weekend.