Borussia Monchengladbach top scorer Marco Reus could miss their league game at Kaiserslautern on Saturday after picking up an adductor muscle injury in training this week.
Coach Lucien Favre said it was not clear whether Reus, who has scored 13 league goals this season, would be fit in time for Saturday despite a medical check in Munich on Thursday.
"We hope he can play but we cannot say that yet," Favre told reporters. Defender Martin Stranzl is also doubtful after suffering an ankle injury in training on Wednesday.
Surprise package Gladbach are third in the Bundesliga, three points behind leaders Borussia Dortmund.
Bayern Munich coach Jupp Heynckes heaped praise on Austria international David Alaba ahead of their trip to Freiburg on Saturday after the 19-year-old midfielder successfully filled in for injured Bastian Schweinsteiger in the last two games.
"He has done a great job in integrating. He has been outstanding," Heynckes told reporters on Thursday.
"He has matured and developed as a player," Heynckes said of the teenager, who joined in 2008 from Austria Vienna. "He is hungry, hard-working and ambitious. He will go far."
Bayern are second in the Bundesliga, two points behind Dortmund.
Cologne have included Slovenia international Miso Brecko in their squad to face Nuremberg on Saturday, despite fining the player a reported 25,000 euros earlier in the week for parking his car on tram tracks while drunk.
"He is in the squad," said Cologne coach Stale Solbakken.
Brecko, who has apologised for driving his vehicle on to the tracks early on Tuesday after leaving a carnival party in the city, was fined for "unprofessional behaviour," the club said.
