Bayern Munich coach Carlo Ancelotti has expressed his unhappiness with Chile over the injury to Arturo Vidal that threatens to keep him out of Friday's Bundesliga match against Mainz.

Midfielders Vidal and Xabi Alonso are both injury doubts with Ancelotti set to decide whether they can play after their final training session.

Vidal has been working his way back to fitness after he picked up an injury on international duty with Chile last month.

He was first injured in their goalless draw against Colombia on November 10, but started in their 3-1 win over Uruguay five days later, angering Bayern bosses.

'He is still struggling with that injury. I have to see him in training today before deciding,' Ancelotti told reporters.

'I am not happy with the Vidal situation. It is normal for a club to release a player for international matches. What I do not see as normal is that Vidal also played in the second match for Chile.'

Ancelotti did not give any details about Alonso's injury but said he had been struggling for the past few days.

The German champions, chasing a record-extending fifth consecutive league crown, have slipped to second place, three points behind promoted RB Leipzig, after a bad run in recent weeks. 

The Bavarians, who have also qualified for the Champions League knockout stage, lost the Bundesliga lead to Leipzig two matchdays ago and Ancelotti said it was crucial to reclaim it on Friday.

Leaders Leipzig, three points clear, are in action against Schalke on Saturday.

'Obviously this is a good time to take over again as leaders,' Ancelotti said. 'It is important to be top as soon as possible but even more important to be there on the final matchday.'