Alcaraz sweats on ankle injury after opening win in Japan; Sinner downs Cilic to launch China Open title bid

World number one Carlos Alcaraz is sweating on his fitness at the Japan Open after injuring his ankle in a 6-4, 6-2 opening win over Argentina's Sebastian Baez on Thursday.

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US Open champion Alcaraz crumpled to the ground chasing a shot in the fifth game of the opening set in Tokyo and sat on the court grimacing for several minutes.

The Spaniard had his left ankle heavily strapped during a medical timeout before gingerly returning.

He soon began to move comfortably and broke world number 41 Baez to take a 5-4 lead.

The match was then delayed for a further half an hour as organisers closed the stadium roof with rain falling.

Six-time Grand Slam champion Alcaraz returned strongly and closed out the first set before breezing past Baez in the second.

The Spaniard was unclear afterwards as to the extent of the injury, saying "if it can affect the rest of the tournament, I don't know".

"It's going to be an important day and a half that Ihave ahead for me before the next match," he said.

"We will see what happens. I will do whatever it takes to be in good shape and ready to play in the next round."

Alcaraz is playing at the Japan Open for the first time and the crowd gave him a warm cheer as he emerged in a burgundy sleeveless outfit.