Schalke 04's Klaas-Jan Huntelaar and Jermaine Jones could miss their Bundesliga match at home to leaders Bayern Munich on Saturday with the former suffering from a cold and the U.S international still nursing an ankle injury.
Huntelaar, last season's top Bundesliga scorer who also grabbed the winner in their 2-1 Champions League victory at Olympiakos on Tuesday, missed training along with Jones on Thursday.
"It will be tight getting them ready to Saturday," coach Huub Stevens told reporters.
The Dutch coach also said Romanian Ciprian Marica was recovering from a groin injury but would not be fit in time for the game.
Schalke are two points behind Bayern, who lead the standings with a maximum nine points from three games.
VfL Wolfsburg goalkeeper Diego Benaglio could play at home to promoted Greuther Fuerth on Saturday despite suffering a minor concussion this week, coach Felix Magath said.
The Swiss international was injured in training on Wednesday.
"Diego Benaglio had some problems the night after his injury and had to see the doctor. But his chances of playing are good," Magath told reporters.
Hamburg SV central defender Jeffrey Bruma is doubtful for Saturday's league match at home to champions Borussia Dortmund with his team looking for their first points of the campaign.
Bruma is suffering from an inflammation in his knee, coach Thorsten Fink said, adding it would be decided late on Friday if he could play.
Hamburg, the only team in the Bundesliga never to have played in the second division since the top league's creation in 1963, have lost their first three games this season and are in 17th place just above Hoffenheim on goal difference.
