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.
"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."
"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.
