Bayern Munich manager Jupp Heynckes has revealed that James Rodriguez "didn't know the score at half-time" of Saturday's 2-1 defeat against Borussia Moenchengladbach after suffering a concussion.
The Colombian midfielder was forced to withdraw after a knock to the head and was replaced by Marco Friedl at the interval.
James was pictured receiving treatment in the first-half after having collided with Gladbach's Tony Jantschke.
The Colombian international was reportedly fine after the game, although Jantschke was taken to hospital.
"James Rodriguez has a concussion most likely," said Heynckes. "He didn’t even know the score at halftime. But we have to wait for the diagnosis of the doctors."
It remains to be seen how long the 26-year-old will be out of action, with Bayern set to host Hannover 96 on Saturday.
James, at Bayern on a two-year loan from Real Madrid, had started to find some form after a difficult start to life in Bavaria.
"With James you have to be patient and handle expectations," club legend Lothar Matthäus told Bundesliga.com prior to the Gladbach loss.
"He has a lot of quality, but he needs time. Let’s not forget he did not have a rhythm at Real Madrid. We have to wait for it, give it time.
"The good thing is that he has already shown some of the things that we have been waiting to see. Against Schalke and RB Leipzig he played a couple of very good games and soon that will be the standard. I think we will soon see that level of performance every week."