Toto Wolff has admitted he is concerned about Valtteri Bottas.

Wolff, the Mercedes team boss, says the Finnish driver was having a good season until he had to start taking a back seat to Lewis Hamilton's title charge.

"Valtteri was very good until then," Wolff said in Abu Dhabi.

"I believe that when you have no more chances in the championship, it hurts you mentally."

On top of that have been rumours that, for 2020, Mercedes has reserved Bottas' race seat for Esteban Ocon.

It could mean Bottas is set to struggle psychologically through 2019 as well.

"I hope that is not what is happening," Wolff said.

"He assures me otherwise, as he is a real Finnish warrior, but now we have to get him back on his feet and in good shape."

Bottas admitted that he is glad a difficult 2018 season for him is now over.

"The season did not go as I would have liked, so I'm pretty happy that it's over," he said in Abu Dhabi.

"Now I need some time to think about things. Mentally it's been a tough year."