Carlos Alcaraz has withdrawn from the Swiss Indoors Basel due to a left foot injury and muscle fatigue to his lower back, he confirmed on social media Wednesday.

“Unfortunately I will not be able to play in Basel this year! 🥲” Alcaraz posted on Instagram. “I have a problem with the plantar fascia in my left foot and muscle fatigue in my lower back which need treatment so I can play the rest of the season. I hope to see you all soon! @swissindoorsbasel_official”

One year ago, Alcaraz made his Basel debut. He earned three wins before losing to eventual champion Felix Auger-Aliassime in the semi-finals.

Alcaraz owns a 63-9 record this season including six titles, with two coming at ATP Masters 1000 events (Indian Wells and Madrid) and another at Wimbledon. The 20-year-old last competed in Shanghai, where he lost in the Round of 16 to Grigor Dimitrov.

The Spaniard is entrenched in a battle for ATP Year-End No. 1 presented by Pepperstone with Novak Djokovic. Had Alcaraz won Basel and the 500 points that come with it, he would have entered the Rolex Paris Masters tied with Djokovic in the Pepperstone ATP Live Race To Turin.

Instead, Djokovic will retain the edge in the battle for year-end No. 1, an honour the Serbian has earned a record seven times. Last year, Alcaraz became the youngest year-end No. 1 in Pepperstone ATP Rankings history.